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    LEVAMISOLE

    1.  EXPLANATION

         Levamisole is a broad spectrum anthelminthic drug widely used to
    control internal parasites in livestock.  It is the levoenantiomer of
    tetramisole.  Optical resolution of d,l- tetramisole into its dextro-
    and levoisomers revealed the levo form to have more anthelminthic
    activity; thus this isomer is used as the anthelminthic.  Levamisole
    can be administered orally or parenterally, and in cattle dermally. 
    Depending on the parasite and host animal the therapeutic dose levels
    vary between 5 and 40 mg/kg body weight.

         Levamisole is used in human medicine as an anthelminthic in a
    single dose form at 2.5 mg/kg.  It is also used for a variety of other
    indications including adjuvant therapy in cancer treatment.  It is
    anticipated this use will expand due to results in recent clinical
    trials.

         Levamisole has not been evaluated previously by the Joint FAO/WHO
    Expert Committee on Food Additives.  The structure of levamisole is
    shown in Figure 1.

    FIGURE 1

    2.  BIOLOGICAL DATA

    2.1  Biochemical aspects

    2.1.1  Absorption, distribution, and excretion

         Distribution of 3H-levamisole was studied in Charles River CD
    cobs rats and C3H black mice.  The rodents were given a single oral
    dose of 2.5 mg/kg and serially sacrificed at 0.5, 1, 4, 8, 16, 24, 48,
    72, 96 hours and 8 days.  Distribution was evaluated using whole body
    sagittal sections. The highest activity was present 30 minutes after
    dosing in both species. The liver concentrated the highest activity in
    both species, with trace amounts remaining in liver 4 days after
    dosing.  A high level of activity was found in bile in the mouse.  A
    significant binding to melanin was also suggested in the mouse (Benard
    et al., 1980).

         Radiolabelled levamisole was administered orally to rats to study
    absorption, distribution, and elimination of the drug.  Groups of 5
    rats were administered a single bolus of 15 mg/kg levamisole via
    gavage.  Rats were then housed in individual metabolism cages for the
    duration of the study.  Four different radiotracers were used:  14C
    in the 8 position was primarily used, while 14C in the 6 position,
    35S, and 3H on the para position of the phenyl ring were used to a
    lesser extent.  The radiolabel was monitored for 8 days following dose
    administration.

         Radioactivity was rapidly absorbed, distributed throughout the
    body, and eliminated via urine and faeces.  An estimated 91% of the
    dose was recovered during the 8 days.  The other 9% was attributed to
    experimental error rather than loss to unidentified pathways. 
    Approximately 40% of the dose was excreted in the urine within 12
    hours; however, further renal elimination was limited, with only about
    48% of the total dose excreted via this pathway.  About 41% of the
    dose was eliminated in faeces, primarily during the initial 48 hours. 
    About 0.9% of the dose was retained in the tissues after 8 days.  The
    highest tissue levels were found in liver and kidney.  At 48 hours 0.8
    and 0.57 ppm were found in liver and kidney respectively (Gatterdam
    et al., 1966 and Boyd et al., 1973).

         Total radioactivity and drug concentrations were determined in
    plasma, organs and excreta of male Sprague-Dawley rats given a single
    oral or intramuscular dose of 7.5 mg/kg of 3H-levamisole.  Rats were
    sacrificed and tissues collected at 1, 4, 8, and 24 hours after
    dosing.  Excreta were collected at 4, 8, 12, 24, 32, 48, 56 and 72
    hours.  A separate group of rats was used for bile duct cannulation.

         Only 45% of plasma radioactivity at one hour was levamisole. 
    During the initial 24 hours following administration the intestinal
    tract contained the largest fraction of the dose regardless of route

    of administration.  Most of the radioactivity was excreted in urine
    (68-78%) rather than the faeces (17-33%) during the initial 72 hours. 
    More than 50% was excreted in urine during the first 12 hours.  Only
    6.3-8.5% of the urine fraction was levamisole, while 5.8 - 8.0% was
    the 4-hydroxylevamisole metabolite.  Biliary excretion was 26% for i.m
    administration but 13% for oral administration (Galtier et al.,
    1983).

         The absorption of levamisole was studied in 3 New Zealand white
    rabbits after a single dose of 10 mg/kg given by gavage.  Peak plasma
    levels of 0.25 ppm were obtained at 30 minutes, while plasma half-life
    was 425 minutes.  At 4 hours plasma levels were <0.01 ppm (Michiels
    et al., 1978).

    2.1.2  Biotransformation

         Metabolites from administration of levamisole to rats were
    evaluated using TLC.  Over 50 distinct metabolites were determined;
    however, the qualitative pattern in urine, faeces, and tissue extracts
    was nearly the same.  Evaluation of metabolites suggests there are
    four initial metabolic processes, each giving rise to a family of
    metabolites (Figure 2).  The most important quantitatively is (1) the
    oxidative introduction of a double bond into the imidazole ring,
    accompanied by or followed by oxidation of the sulfur to sulfoxide and
    introduction of a hydroxy group in the para position of the phenyl
    ring.  The second most important pathway (2) is the hydrolysis of the
    thiazolidine ring to an oxoimidazole metabolite.  The third (3)
    pathway is formation of p-hydroxytetramisole and its subsequent
    conjugation with glucuronic acid.  The least important pathway is (4)
    the hydrolysis of the thiazole ring to yield the mercaptoethyl
    intermediate and subsequent oxidation to sulphoxide and sulphone.  The
    metabolic pattern suggests these are not the only pathways involved,
    with about 20% of the metabolites remaining unidentified.  The
    metabolic scheme depicted in Figure 2, with the various pathways, has
    been proposed based on this information (Gatterdam et al., 1966
    and Boyd et al., 1973).

    2.1.3.  Pharmacokinetics

         Three healthy male volunteers each received a single oral dose of
    150 mg 3H-levamisole.  Peak plasma levels of levamisole were reached
    2-4 hours after dosing.  Parent drug represented 40% of total
    reactivity.  Total radioactivity and unchanged levamisole were
    measured in plasma, urine and faeces for 72 hours post-dosing.  The
    half-life of levamisole was 4 hours while the half life for total
    reactivity was 16 hours.  The primary route of excretion was via urine
    - 70% - while only 3-5% appeared in the faeces.  About 4% of the
    excreted material was parent compound compared with the remainder
    being metabolites (Heykants, 1976).  A more recent study is in
    agreement with this data (Kouassi et al., 1986).

    2.2  Toxicological studies

    2.2.1  Acute toxicity studies

         The results of acute toxicity studies with levamisole are shown
    in Table 1.

    2.2.2  Short-term studies

    2.2.2.1  Rats

         Sixty Alderley Park albino rats were divided into groups of 10
    rats/sex/dose and received 0, 50 or 100 mg/kg body weight daily via
    gavage for 30 days.  Clinical signs, weight, haematology, and
    urinalysis were monitored at intervals during the study. At sacrifice,
    gross necropsy was performed and organ weights were determined. 
    Tissues were examined histopathologically.  A moderate reduction in
    weight gain occurred in treated groups.  An increase in liver and
    kidney weights of treated rats also occurred (Davey, 1968a).

         Six to eight week old Wistar rats were divided into 4 groups of
    10 rats/sex/dose and received target doses of 0, 10, 40, or 160 mg/kg
    b.w./day levamisole in the feed at rates of 0, 100, 400, or 1600 ppm
    daily for 13 weeks.  The following parameters were monitored: 
    survival, behavior and appearance, food consumption (weekly), body
    weight (weekly), haematology (terminal), clinical chemistry
    (terminal), urinalysis (terminal), organ weight, and gross pathology
    and histopathology.  Survival and clinical signs were not effected by
    treatment.  Food consumption was decreased in the 160 mg/kg b.w./day
    group, while weight gains were reduced in all female treatment groups
    and the 40 and 160 mg/kg b.w./day male treatment groups.

         Haematology, clinical chemistry, and urinalysis of treated groups
    were normal except for elevated urine pH.  Organ weights were in
    general reduced in the 160 mg/kg b.w./day group.  No treatment-related
    histopathologic changes were observed (Marsboom et al., 1969).

    2.2.2.2  Dogs

         Levamisole was administered to 10 beagle dogs orally at the rate
    of 15 mg/kg b.w./day in three divided doses of 5 mg/kg body weight. 
    Drug related vomiting was observed in two dogs (Desplenter, 1983).

    FIGURE 2

    Table 1:  Results of acute toxicity studies with levamisole
                                                                      
    Species    Sex     Route       LD50          Reference
                                   (mg/kg)
                                                                      

    Mouse      M&F     oral        205-285       Davey, undated a
                                                 Niemegeers, 1975

               M&F     i.v.        20-28         Davey, undated a
                                                 Niemegeers, 1975

               M&F     s.c.        102-121       Davey, undated a
                                                 Niemegeers, 1975

    Rat        M&F     oral        458-1095      Davey, undated a
                                                 Niemegeers, 1975

               M&F                 286-566       Wallwork &
                                                 James, 1975

               M       i.v.        17-28         Davey, undated a
                                                 Niemegeers, 1975

               M&F     s.c.        81-89         Davey, undated a
                                                 Niemegeers, 1975

                       dermal      252           Wallwork & James,
                                                 1975

    Rabbit     M       oral        458           Davey, undated a

               F       i.v.        25            Davey, undated a

    Swine      M&F     oral in     no            Wang, 1970a
                       feed at     lethality
                       40 mg/kg

                                                                      

         A one month oral study with levamisole was conducted in beagles. 
    Twenty-four dogs were divided into 3 groups containing 4 dogs/sex. 
    Dogs received 0, 10, or 20 mg/kg b.w./day.  Clinical signs included
    ataxia and convulsions; one death occurred in the high dose group. 
    Treated groups lost weight during the study.  Haematologic and
    clinical chemistry parameters were evaluated but no treatment-related
    effects occurred.  Gross necropsy was performed on all dogs and organ
    weights were obtained.  Histopathologic evaluation was generally
    unremarkable although some lymphoid cuffing occurred in the cerebral
    vessels of high dose dogs (Davey, 1968b).

         Groups of beagle dogs (2/sex) received 0, 1.5, 3, or 6 mg/kg
    b.w./day of levamisole daily for 90 days.  Dogs were up to two years
    of age at study initiation.  Parameters evaluated included:  clinical
    signs, food intake, body weight, haematology, clinical chemistry,
    organ weights and histopathology (6 mg/kg b.w./day group only was
    sacrificed).  Special emphasis was placed on evaluation of possible
    haemolytic effects of levamisole.  Dogs were distributed into dose-
    groups based on predetermined susceptibility to erythrocyte
    haemolysis.  Methaemoglobin and erythroblastosis were monitored.  No
    treatment-related effects were observed (Huchison et al., 1967).

         The effect of levamisole treatment for one year in dogs was
    evaluated. Four groups of 8-10 month old beagles containing 3
    dogs/sex/group were administered levamisole orally in gelatin capsules
    daily six times/week for 12 months.  Dogs received 20, 5, or 1.25
    mg/kg b.w./day levamisole or 250 mg lactose.  Dogs were acclimated and
    baseline parameter values obtained during a 6 week period prior to
    dosing.  The following parameters were evaluated:  Clinical signs
    including ophthalmoscopy (0, 6, and 12 months), ECG and blood pressure
    (monthly), food consumption, body weight (weekly), haematology, and
    clinical chemistry and urinalysis (monthly).  Gross pathology and
    organ weights were monitored at necropsy, and histopathologic
    examination was performed on a standard array of tissues.

         During the 8th week all 20 mg/kg b.w./day dogs and one 5 mg/kg
    b.w./day female dog experienced severe treatment induced haemolytic
    anaemia.  Decreases in haematocrit, haemoglobin, and RBC count
    occurred with increases in erythoroblasts and immature granulocytes. 
    These dogs were removed from the study.  Their haematology parameters
    returned to normal about 2 weeks after dosing was stopped, but anaemia
    returned when treatment was reinstituted.  An in vitro serum RBC
    agglutinizing factor which required at least 100 g/ml of levamisole
    was demonstrated.  No other treatment-related effects were found in
    this study (Marsboom et al., 1975).

         The effect of levamisole administered daily as a pour on was
    studied in dogs. Twenty-four beagles were divided into 4 groups of
    3/sex and received 0, 2.5, 10, or 40 mg/kg b.w. daily as a 20%
    solution applied to the back.  The following parameters were
    evaluated:  clinical signs, ophthalmoscopic examination, body weight,
    heart rate and ECG, blood pressure, haematology, clinical chemistry,
    urinalysis, and at necropsy organ weights, gross pathology and
    histopathology.  Significant weight loss occurred in the 40 mg/kg
    b.w./day group.  No other treatment-related effects were observed in
    this study (Verstraeten et al., 1983).

         A series of clinical reports on levamisole-associated haemolysis
    in dogs were evaluated.  All reports were related to long-term use of
    levamisole for dirofilaria treatment.  The dose regimens generally
    were altered at two week intervals with peak doses of 10-24 mg/kg

    b.w./day and low doses of 2-3 mg/kg b.w./day.  Anaemia developed at 3-
    6 weeks of treatment (Maes & Marsboom, 1988; Atwell et al., 1981).

    2.2.2.3  Pigs

         Levamisole-HCl was administered to pigs at the rate of 0, 8, 24,
    and 40 mg/kg body weight in feed or drinking water as a single
    treatment.  Five pigs/sex/dose were treated with each route of
    administration.  The treatment was repeated one week later.  More
    severe signs were observed in the drinking water group.  Salivation
    and vomiting were dose-related, while tremor, tachypnoea, transient
    recumbency and 10% mortality were observed in the 40 mg/kg body weight
    group.  Salivation and vomiting only were observed in the 40 mg/kg
    body weight feed-route pigs.  Some suggestion of hepatic toxicity was
    found upon histopathologic evaluation.  The authors concluded that,
    although some toxicity occurred, the 40 mg/kg body weight feed-
    treatment and 24 mg/kg body treatment water-treatment were safe for
    swine based on reversibility of clinical signs and hepatic lesions
    (Wang, 1970b).

    2.2.2.4  Primates

         A 23 kg male baboon was treated dermally with 10, 20, and 40
    mg/kg body weight levamisole with intervals of 10 and 4 days between
    treatments.  Effects including minor excitement were observed
    following the 40 mg per kg body weight dose (Desplenter, 1980).

    2.2.3  Long-term/carcinogenicity studies

    2.2.3.1  Mice

         An oral carcinogenicity bioassay of levamisole was conducted
    using albino Swiss mice.  Four hundred 7 to 8 week old mice were
    divided into 4 groups containing 50 mice/sex.  Following an
    acclimatization period of one week, levamisole was provided at the
    rate of 0, 12.5, 50, and 200 ppm in drinking water for 18 months to
    provide target doses of 0, 5, 20, and 80 mg/kg b.w./day based on
    consumption of 100 ml/week/mouse.  The test article was stored at room
    temperature in well-closed amber bottles.  Solutions were prepared
    fresh weekly.  The animals were initially housed 25/cage but after 7
    months were housed individually to prevent fighting.  Clinical
    examinations were performed daily except Sundays, but were not
    reported.  Gross necropsy was performed on all mice that died or were
    sacrificed due to moribund condition as well as at study termination. 
    Lung, liver, pancreas, kidney, spleen, testis, epididymis, ovary,
    uterus, mammary gland, adrenals, hypophysis, lymph nodes, and any
    other indicated tissue were examined histopathologically.  Survival
    rates at the end of the study were: 0 ppm - 32%M/22%F, 12.5 ppm -
    20%M/40%F, 50 ppm - 18%M/40%F, and 200 ppm - 20%M/38%F.  However the
    survival rate at 12-14 months was reduced considerably from that

    expected for a useful carcinogenicity bioassay:  less than 50% in all
    male treatment groups and about 40% in the female control group.  No
    treatment-related gross pathology was reported.  No treatment-related
    effects were seen with respect to number of tumour-bearing mice or
    incidence of various tumour types.  However, appropriate tissues
    available for examination were fewer than expected for a
    carcinogenicity bioassay (Vandenberghe et al., 1980).

    2.2.3.2  Rats

         The chronic toxicity of levamisole was examined in rats.  Six to
    eight week old Wistar rats were divided into 4 groups of 20/sex and
    received target doses of 40, 10, 2.5 and 0 mg/kg b.w. levamisole daily
    provided in the feed at rates of 800, 200, 50, or 0 ppm.  Diets were
    prepared weekly.  An interim sacrifice of 10 rats/sex was performed at
    12 months with the final sacrifice at 18 months.  The following
    parameters were evaluated:  Clinical signs (daily), ophthalmoscopic
    exam (terminal sacrifice), food consumption (weekly), body weight
    (weekly), and haematology, clinical chemistry, and urinalysis
    (terminal sacrifice).  Gross necropsy was performed at sacrifice. 
    Organ weights were obtained for heart, spleen, thymus, liver, kidney,
    pancreas, adrenals, thyroid, brain, genital organs, and lung. 
    Histopathology was performed on tissue from the above organs and the
    following array of tissues:  Lymph nodes, urinary bladder, alimentary
    tract tissues, parathyroid, hypophysis, diaphragm, striated muscle,
    tongue, teeth, skin, bone marrow, and eye.  No treatment related
    clinical signs or mortality occurred.  Mean food consumption was
    reduced in both sexes of the high dose group.  Weight gains were
    significantly decreased for both sexes of the high dose group
    throughout the study.  The middle dose group weight gain was generally
    reduced throughout the study but was significant only for the 12 month
    females.  Clinical chemistry parameters which were altered included
    marginal increases in alkaline phosphatase in high dose females, and
    bilirubin in 12 month high dose males and females.  In the high dose
    group the absolute weights of organs generally were decreased, while
    the relative weights were increased.  Histopathologic treatment-
    related changes were limited to a degeneration of the germinal
    epithelium of the testes and a mild chronic stimulation of the liver
    seen only in the high-dose group (Marsboom et al., 1972).

         The tumourigenic potential of levamisole was studied in Wistar
    rats.  Four hundred 3 month old rats were divided into 4 groups of
    50/sex and following a one week acclimatization period were provided
    levamisole in the diet at rates of 0, 50, 200, or 800 ppm to provide
    target doses of 0, 2.5, 10, or 40 mg/kg b.w./day.  Test diet was
    prepared every two weeks.  Animals were examined daily but clinical
    signs were not reported.  A full necropsy was performed on all
    surviving animals at 24 month study termination and all animals which
    died or were sacrificed due to moribund condition during the study. 
    The following tissues were examined histopathologically:  Lung, liver,

    pancreas, kidney, spleen, testis, epididymis, ovary, mammary gland,
    adrenals, thyroids, parathyroids, hypophysis, lymph nodes, and any
    other indicated tissue.  Survival rates for the various groups were: 
    0 ppm - 4%M/10%F, 50 ppm - 2%M/8%F, 200 ppm - 2%M/20%F, and 800 ppm -
    6%M/14%F.  Survival rates for all male study groups were well below
    50% by 16 months.  No treatment-related effects were seen with respect
    to number of tumour-bearing rats or incidence of various tumour types. 
    However, appropriate tissues available for examination were fewer than
    expected for a carcinogenicity bioassay (Marsboom & Herin, 1980).

    2.2.4  Reproduction studies

    2.2.4.1  Rats

         The effect of levamisole administered prior to breeding for 60
    days in males and 14 days in females on the reproductive performance
    of rats was studied.  To accomplish the study 320 sexually mature
    Wistar rats were divided into groups of 20 rats/sex and received
    levamisole target doses of 1.25, 5, 20, or 80 mg/kg b.w./day in the
    feed at rates of 25, 100, 400, or 1600 ppm for the prescribed duration
    of treatment.  Fresh diets were prepared weekly.  Treated rats were
    mated with nontreated rats.  No control matings were performed with
    untreated animals.  Matings were validated by daily vaginal washings
    for sperm.  Female weights were determined at insemination and weekly
    thereafter.  Half the pregnant females were sacrificed on gestation
    day 13 and the uterus was examined for number and distribution of
    embryos, and resorptions as well as unusual uterine condition.  The
    remaining females were sacrificed on gestation day 22.  The number and
    distribution of fetuses were recorded and fetuses were examined
    externally.  Fetuses were processed and examined for internal
    abnormalities via clearing and alizarin red staining of bones and
    serial sectioning as well as X-ray analysis.  No treatment-related
    effects on male or female fertility or offspring normality were
    reported in this study (Marsboom, 1969a).

         The potential toxicity of levamisole administered during the
    peri- and post-natal periods was evaluated in female Wistar rats. 
    Five groups of 20 three month old rats received 0, 25, 100, 400, and
    1600 ppm levamisole in the diet from gestation day 16 through the 3
    week lactation period to provide target doses of 0, 1.25, 5, 20, and
    80 mg/kg b.w./day.  Female weights were recorded on gestation days 1,
    7, 14, and 21 post parturition, and on lactation days 14 and 21.  Live
    and dead pups were examined, counted, and weighed a few hours after
    parturition.  Females not delivering by gestation day 24 were
    sacrificed, necropsied, and uteruses evaluated for distribution of
    placental sites, resorptions and fetuses.  Surviving pups were weighed
    on lactation days 14 and 21.  There was a decrease in weight gain for
    the 1600 ppm dams.  Additionally an increased incidence of stillborn
    pups, reduced birth weight, reduced lactational weight gains, and
    decreased 3-week survival rate were recorded for the 1600 ppm pups
    (Marsboom, 1969b).

         The potential embryotoxic and teratogenic effects of levamisole
    were evaluated during the gestation periods of three consecutive
    generations of treated pregnant rats.  Eighty virgin 3-4 month old
    rats were divided into 4 groups of 20 rats each and provided
    levamisole at the rate of 0, 100, 400, and 1600 ppm in the diet,
    equivalent to 0, 5, 20 and 80 mg/kg body weight/day on gestation days
    6-15.  Prior to and after the period of organogenesis the rats were
    provided the control diet.  At the age of 3 months 80 virgin females
    were selected from those born to treated mothers of the prior
    generation and mated with 40 non-littermate males also born to treated
    dams from the preceding generation.  The males were treated in the
    same manner as their dams.  The succeeding generation was established
    in the same manner except that dams were sacrificed on gestation day
    22 for evaluation of teratogenic and embryotoxic parameters.  Females
    were weighed on the 1st, 7th, 14th and 21st days of gestation, while
    pups were weighed shortly after parturition and on lactation days 4,
    14, and 21.  If parturition had not occurred by gestation day 24 rats
    were sacrificed, necropsied and distribution of fetuses and
    resorptions were noted.  The litters from the 3rd generation were
    examined for distribution of live and dead fetuses and resorptions. 
    All fetuses were examined for external abnormalities, radiographic
    examination was carried out, and fetuses were processed for soft
    tissue (1/3) and skeletal (2/3) examination.  No treatment-related
    effects were recorded on dams or fetuses (Marsboom, 1974).

    2.2.5  Special studies on embryotoxicity/teratogenicity

    2.2.5.1  Rats

         The potential embryotoxicity or teratogenicity of levamisole was
    studied in Wistar rats.  Sexually mature female Wistar rats were mated
    with fertile males and received target doses of 0, 1.25, 5, 20, or 80
    mg/kg b.w./day levamisole based on 25, 100, 400, and 1600 ppm
    levamisole in the diet on gestation days 6-15.  Mating was established
    by vaginal plug.  Weights of females were obtained at mating and
    weekly thereafter.  Food consumption was recorded individually during
    gestation.  Females were sacrificed on gestation day 22 and the
    following litter and fetal parameters obtained:  Number and
    distribution of live and dead fetuses and resorptions within
    abnormalities (external - all fetuses, skeletal - 2/3 and soft
    tissue - 1/3).  At 1600 ppm the incidence of resorptions increased
    slightly.  No other parameters were effected (Marsboom, 1972).

         A teratology study with levamisole at doses of 0, 10, 50, and 100
    mg/kg body weight/day was carried out on rats.  Female rats were
    divided into 4 groups of 20 rats and received levamisole on gestation
    days 0-20 by mouth.  Half the females were sacrificed on day 20,
    litters were examined grossly, fetuses cleared and stained with
    alizarin red and examined for skeletal effects.  The remaining females
    littered and reared their litters to lactation day 21.  Maternal

    weight gain was reduced in a dose-related manner.  No effect on litter
    parameters, embryotoxicity or post natal growth was observed (Davey,
    undated c).

    2.2.5.2  Rabbits

         The teratogenic potential of levamisole was studied in rabbits. 
    Sixty mature female New Zealand rabbits were divided into 3 groups of
    20 rabbits each.  Rabbits were inseminated artificially due to low
    pregnancy rate in the rabbit colony.  Does received 0, 10 or 40 mg/kg
    b.w./day levamisole by gavage on gestation days 6-18.  Does were
    observed daily for toxicity and weights were recorded at insemination,
    gestation days 6-18, and at sacrifice.  Rabbits were sacrificed on
    gestation day 28, and necropsied.  Fetuses were examined grossly and
    then processed for soft tissue examination (1/3) or skeletal
    examination (2/3).  Survival of does was not affected by treatment. 
    There was a marked reduction in mean weight gain in the 40 mg/kg
    b.w./day group compared with controls (250 vs 432, respectively).  The
    incidence of resorptions and dead fetuses was doubled in the 40 mg/kg
    b.w./day group vs controls (10 vs 5), while the incidence of litters
    with abnormalities was 4 in the 40 mg/kg b.w./day group vs 0 in the
    control and 10 mg/kg b.w/day groups.  However, this was within the
    historical control range.  No treatment-related effects from
    levamisole occurred in this study (Marsboom, 1972).

         Nineteen female Dutch rabbits were divided into 3 groups of 6-7
    rabbits each to evaluate the potential teratogenic effect of
    levamisole.  Rabbits received 0, 25, or 75 mg/kg b.w. orally
    throughout the gestation period.  Does were sacrificed on gestation
    day 28 and litter parameters evaluated.  After examination the fetuses
    were processed for skeletal examination.  No treatment-related effects
    were reported (Davey, undated c).

    2.2.5.3  Pigs

         Twenty pregnant sows received 10 mg/kg body weight levamisole 4
    times at 2-day intervals intramuscularly.  A group of 20 untreated
    sows served as controls.  The sows were selected to have produced one
    previous litter of >7 pigs.  The sows were divided into 4 groups of
    5 each and received treatment on gestation days 8-14, 16-22, 24-30, or
    32-38.  Parturition data, length of gestation, litter size, sex,
    weight, suckling behavior and external abnormalities were evaluated. 
    No treatment-related embryotoxic or teratogenic effects occurred in
    this study (Veys & Dony, 1985).

    2.2.6  Special studies on genotoxicity

         The results of genotoxicity studies with levamisole are
    summarized in Table 2.

    2.3  Observations in humans

         The safety of levamisole use in humans has recently been
    reviewed.  Levamisole has been used in humans for the following
    indications:  anthelminthic, rheumatoid arthritis, inflammatory
    disease, infectious disease, and cancer therapy.  Aside from its use
    for parasitic infection, these uses appear to be based on the
    immunomodulating properties of levamisole.  Although a number of side
    effects have been reported, the most important are haematologic,
    including reversible leukopenia, agranulocytosis, and
    thrombocytopenia.  A low incidence of agranulocytosis appears to occur
    in all continuous dose regimens ranging from 50 to 200 mg daily and
    with 3 days treatment every other week to continuous therapy. 
    Haematologic effects were seen in nearly 5% of rheumatic patients but
    only 0.2% of infectious patients.  Based on his review of the data,
    the author concluded that agranulocytosis was dose-related in onset
    (Reyntjens, 1989).

         A survey of published literature on levamisole-associated
    agranulocytosis identified 110 citations.  These reports occurred
    between 1973 and 1984, and, based on volume of levamisole uses,
    agranulocytosis correlated closely with human use of levamisole for
    immunotherapy but not veterinary use of levamisole (Veys, 1989).

         Numerous clinical reports of levamisole side effects are in the
    literature.  Two reports are reviewed for illustrative purposes:

         Observations were made on a single cancer patient who was given
    only levamisole at the rate of 2.5 mg/kg body weight for 2 consecutive
    days per week for 13 weeks.  The patient developed an agranulocytosis
    and therapy was discontinued.  His total white cell count was 1100
    cells/mm3.  Bone-marrow was described as hypercellular with relative
    erythroid hyperplasia and virtually no myelopoiesis (0.5% myeloblasts,
    no mature neutrophils, 2% eosinophils, 0.5% basophils, 63%
    lymphocytes, 5% plasma cells, 0.5% monocytes, 23.5% erythroid forms,
    and 5% reticulum cells). Megakargocytes were present.  Seven days
    later the patient's bone marrow was hypocellular but demonstrated
    myelopoiesis:  12% myeloblasts, 15% promyelocytes, 2% myelocytes, 8%
    metamyelocytes; and 1% neutrophils. The red cell series was reduced
    and megakaryocytes were markedly reduced.  A transient but severe
    thrombocytopenia (without bleeding) to 30,000 cells/mm3 also occurred
    during the first week.

        Table 2:  Genotoxicity of levamisole

                                                                                          
    Test system       Test Object           Concentration     Results      Reference

                                                                                          
    Chromosomal       Human                 from humans       positive     Berger 
    aberrations       lymphocytes           treated with                   et al., 
                                            150 mg                         1980
                                            levamisole
                                            (in vivo) or
                                            250 g/ml
                                            (in vitro)

    Sister            Humanadded            lymphocyte        positive     Berger
    Chromatid         lymphocytes           cultures from                  et al., 
    Exchange                                untreated                      1980
                                            volunteers

    Ames test         TA 1535               10-10,000 g/ml   negative     Richold
    (+/- S9)          TA 1537                                              et al., 
                      TA 98                                                1979
                      TA 100

    Chromosomal       Cultured              +S9: 5000 g/ml   negative     Enninga,
    aberrations       human                 -S9: 1000 g/ml                1988
    (+/- S9)          lymphocytes

    Micronucleus      Mouse                 3-75 mg/kg        negative     Ikegami,
    test              erythrocytesorally                                   et al., 1981

    Dominant          Male and              Single oral       negative     Marsboom,
    lethal test       female                dose: 10, 40                   1977
                      mice                  or 160 mg/kg
                                            b.w.
                                                                                          
    
         The marrow recovered in 10-14 days with circulating neutrophils
    rebounding to raised levels.  The immunologic basis for these
    levamisole effects were explored using the leuco agglutination test
    and Clq deviation test for circulating immune complexes.  Levamisole-
    dependent leuco agglutinations were present in the patient's serum in
    high titre (1/512) during the acute phase.  During the first week the
    patient's serum induced some spontaneous leuco agglutination; however,
    after one week added levamisole was required for leuco agglutination. 
    Circulating Clq-reactive materials reached a peak seven days after
    onset of neutropenia coincident with the peak in leuco agglutination
    titre (Parkinson et al., 1977).

         A clinical report of a 52 year old female patient with a history
    of current seronegative rheumatoid arthritis, erythema nodosum in
    childhood, and angioneurotic edema at age 35 to 37 years was reviewed. 
    She received 50 mg levamisole once weekly.  After each dose she
    experienced a mild flu-like syndrome.  Following the sixth dose this
    syndrome was more severe and mouth ulcers developed.  This syndrome
    became more pronounced following the seventh dose.  She had a
    polymorph count of 225 per mm3 6 days later.  Bone marrow examination
    showed increased promyelocytes but maturation arrest at the myelocyte
    stage.  Erythropoiesis was normal.  No sideroblasts were present.  A
    dose of 10 mg levamisole was given 2 months later.  No clinical side
    effects were noted but a polymorph decrease of 31% occurred at 24
    hours post dose.  A dose of 25 mg of levamisole two weeks later
    produced clinical signs and a 43% reduction of polymorphs at 32 hours. 
    Twenty leucocyte lines were tested for agglutination with 19/20
    yielding negative results.  Cytotoxicity tests were also negative
    (Felix-Davies, 1978).

         In addition to individual case studies and clinical reports, some
    early epidemiologic reports or reviews of levamisole-associated
    haematologic adverse effects were available.  Adverse reactions in 267
    of 6217 patients on levamisole were analyzed via a questionnaire. 
    Significant reactions were agranulocytosis (2.3%), skin rash and
    febrile illness.  These occurred primarily in patients (particularly
    females) with rheumatoid arthritis.  Agranulocytosis was spontaneously
    reversible (Symoens et al., 1978).  A low incidence of leukopenia
    and agranulocytosis (0.4%) was reported after use of levamisole
    adjuvant therapy in 203 neoplastic patients (Colizza et al.,
    1981).  Forty-six controlled studies (2635 patients) of adjuvant
    levamisole treatment in cancer were reviewed with respect to efficacy
    and incidence of agranulocytosis.  More patients receiving levamisole
    for 2 consecutive days every week developed agranulocytosis (3.1%)
    than those receiving it for 3 days every other week (0.1%).  Dose
    regimens were in the 5 -200 mg/kg range (Amery & Butterworth, 1983).

         The pathogenesis of levamisole-associated agranulocytosis has
    been studied.  Based on levamisole's immunomodulating properties,
    these efforts have focused on immunologic parameters.  Serum from 10
    neutropenic patients and 10 normal patients receiving levamisole was
    evaluated.  All 10 neutropenic patient serums were strongly
    granulocytotoxic.  IgM granulocytotoxic antibodies were identified. 
    None of the control patient sera were granulocytotoxic.  A variety of
    other immunologic parameters were evaluated.  Tests for a hapten
    mechanism were negative (Thompson et al., 1980).  Three
    neutropenic patients receiving levamisole were found to have
    complement-dependent granulocytotoxic antibodies.  The agranulocytosis
    appeared to be related to auto-antibodies since serum
    granulocytotoxicity correlated closely with agranulocytosis (Drew
    et. al., 1980).  More recently the possible similar aetiologies of
    levamisole-induced agranulocytosis in humans and haemolytic anaemia in

    dogs were reviewed.  The authors concluded the evidence is compatible 
    with agranulocytosis in man and haemolytic anaemia in dogs being
    different clinical manifestations of the same immuno-allergic reaction
    (Maes and Marsboom, 1988).  

         A recent review of proposed immunomodulating activity etiologies
    concluded, however, that none of the presently proposed hypotheses
    adequately explains levamisole therapeutic activity (Van Wauwe &
    Janssen, 1989).

    3.  COMMENTS

         The Committee considered results from studies on metabolism,
    short-term studies, studies on carcinogenicity, effects on
    reproduction and development and mutagenicity, and from clinical
    reports in humans.

         The absorption, distribution, excretion, and biotransformation of
    levamisole were studied primarily in rats.  The results showed that
    the drug is rapidly absorbed and metabolized, with only 45% of the
    radioactivity in the plasma being accounted for by the parent compound
    after one hour.  More than 90% of the radioactivity was excreted in
    the urine and faeces within 8 days.  Over 50 metabolites were
    identified from these studies and four major metabolic pathways have
    been proposed.  Following oral administration of levamisole to humans,
    the half-life was estimated to be 4 hours, while the half-life for
    total radioactivity was 16 hours.  Most of the radioactivity was
    excreted in the urine, with 4%  as unchanged levamisole and the
    remainder as metabolites. 

         In a 13-week study in rats, in which levamisole was administered
    in the diet, reduced weight gains were noted at doses of 40 and 160
    mg/kg b.w./day in both sexes.  This effect was also observed at 10
    mg/kg b.w./day in female rats.  In a 90-day study in dogs, no drug-
    related effects were noted at doses of up to 6 mg/kg b.w./day.

         Groups of three dogs of each sex were dosed for one year (six
    days per week) by oral administration of the compound in capsules. 
    During the eighth week, all six dogs that received levamisole at 20
    mg/kg b.w./day and one dosed at 5 mg/kg b.w./day developed severe
    haemolytic anaemia.  The haematocrit level and total erythrocyte
    counts were decreased while the number of erythroblasts and immature
    granulocytes were increased.   Treatment was discontinued in these
    affected dogs, and their haematological parameters returned to normal
    about two weeks later.  However, anaemia developed again when
    treatment was resumed.  A levamisole-dependent erythrocyte-
    agglutinating factor was demonstrated in vitro in the serum of these
    dogs.  No other treatment-related effects were found.  The no-
    observed-effect level was 1.25 mg/kg b.w./day in this study.

         The Committee noted the deficiencies in the study, including the
    low number of animals per group, completion of the study with only two
    treated groups and uncertainty regarding the mechanism for levamisole-
    induced haemolysis, which appeared to have an immunological basis.

         In a chronic toxicity study in rats in which levamisole was
    administered in the diet for 12 or 18 months, a significant reduction
    in weight gain was observed at 80 mg/kg b.w./day in both sexes.  This
    effect occurred to a lesser degree at 20 mg/kg b.w./day.  In general,
    absolute organ weights were generally decreased, while relative organ

    weights were increased at 80 mg/kg b.w./day.  Other changes observed
    in this treatment group included slight increases in alkaline
    phosphatase (in females) and bilirubin (at 12 months), and
    degeneration of the germinal epithelium of the testis.  The no-
    observed-effect level in this study was 20 mg/kg b.w./day.

         In an 18-month carcinogenicity study in mice in which levamisole
    was administered in drinking-water, no treatment-related effects were
    evident with respect to the number of tumour-bearing mice or the
    incidence of various types of tumor.  Dose levels of up to 80 mg/kg
    b.w./day were used in this study, but the Committee noted the lack of
    toxicity data provided to support selection of these doses.  There was
    no evidence for a carcinogenic effect in female mice.  However, the
    survival rate of male mice beyond 12-15 months was poor.  In addition,
    the Committee noted that a high percentage of the male mice had not
    been examined microscopically, which further reduced the sensitivity
    of the study.  The Committee concluded that this study did not fully
    assess the carcinogenic potential of levamisole in male mice.

         In a 24-month carcinogenicity study in rats in which levamisole
    was administered in feed at doses up to the equivalent of 40 mg/kg
    b.w./day, no treatment-related effects with respect to the number of
    tumour-bearing rats or incidence of various tumour types were
    reported.  There was no evidence of a carcinogenic effect in female
    rats and survival was not affected by treatment.  However, taking into
    account low survival rate beyond 18 months, the Committee concluded
    that this study did not fully assess the carcinogenic potential of
    levamisole in male rats.

         In three reproduction studies in rats in which levamisole was
    administered in the diet, there was decreased maternal weight gain,
    increased incidence of still birth, reduced birth weight, and reduced
    weight gain by the pups during suckling, and decreased survival at 3
    weeks at 80  mg/kg b.w./day.  The no-observed-effect level for effects
    on reproduction was 20 mg/kg b.w./day.

         Levamisole was further evaluated for effects on development in
    studies in which it was administered to rats and rabbits during all or
    part of gestation.  In rats the incidence of resorptions was increased
    slightly after oral administration at 80 mg/kg b.w./day, which was the 
    highest dose tested.  In the rabbit, the highest dose  of 40 mg/kg
    b.w./day caused a marked reduction in maternal weight gain, and an
    increase in the  incidence of fetal death and abnormalities.  The no-
    observed-effect levels for these studies were 20 mg/kg b.w./day for
    the rat and 10 mg/kg b.w./day for the rabbit.

         The genotoxic potential of levamisole was investigated in a
    number of test systems.  Positive results were reported in the
    chromosomal aberration test and the sister chromatid exchange test
    using human lymphocytes.  Negative results were reported in a series

    of Ames tests, a further chromosomal aberration test, a mouse
    micronucleus test, and a dominant lethal assay. 

         The Committee considered data from numerous clinical reports on
    the use of levamisole in human therapy.  Adverse effects were rare,
    the most important being agranulocytosis and neutropenia.  Although
    these haematological disorders were generally reversible, certain
    factors, such as the concurrent use of other drugs, made the
    interpretation of occasional fatalities extremely difficult. 
    Fatalities were usually associated with concurrent infection before
    agranulocytosis had been recognized.  The Committee noted that the
    increase in the number of IgM antibodies observed in some patients
    suggested an immunological basis for the granulocytopenia; this effect
    was not associated with the single dose of 2.5 mg per kg of body
    weight used for the treatment of human parasites.  Thrombocytopenia
    and haemolytic anaemia have also been reported in patients being
    treated with levamisole.  

         The Committee noted that there were large numbers of published
    reports concerning the induction of granulocytopenia or
    agranulocytosis by levamisole, primarily in patients being treated for
    rheumatoid arthritis or cancer.  However, the data were inadequate for
    the purposes of establishing a no-observed-effect level for induction
    of these haematological effects.  The results of a survey showed a
    0.1% incidence of agranulocytosis in patients receiving levamisole at
    50-200 mg for three days every other week.  However, agranulocytosis
    and thrombocytopenia have been reported in a cancer patient treated
    only with levamisole at 2.5 mg per kg of body weight on two
    consecutive days each week for 13 weeks.  Although the bone marrow was
    initially depressed, the patient's immunological indicators returned
    to normal within two weeks of the cessation of treatment.  The
    immunological basis for this condition was further supported by the
    presence of levamisole-dependent leukoagglutinins correlating with the
    acute phase of granulocytopenia.  A report of a patient with a history
    of prior treatment with levamisole who developed mild granulocytopenia
    following the administration of a single challenge dose of
    approximately 0.2 mg per kg of body weight, suggested that this dose
    may be near the no-observed-effect level in humans.

         The Committee considered that levamisole-induced haemolysis in
    dogs and agranulocytosis in humans may have a similar immunological
    basis.  However, there was insufficient evidence to confirm or exclude
    this possibility.  It was noted that thrombocytopenia and haemolytic
    anaemia have been observed in both dogs and human patients treated
    with levamisole.  However, neither the data from case reports of human
    therapeutic use nor those from the study in dogs were considered
    adequate for the purpose of establishing a full ADI.  In the former
    instance, most of the patients were suffering from cancer or diseases
    associated with underlying autoimmune disorder, and had been exposed
    to a variety of therapeutic regimens before receiving levamisole;

    furthermore, there was no information about the threshold dose at
    which agranulocytosis occurred.  In the study in dogs, which used an
    inadequate number of animals, haemolysis rather than agranulocytosis
    was the end-point, and there was uncertainty whether the pathogenesis
    of this effect was identical to that responsible for the
    agranulocytosis in humans.

    4.  EVALUATION

         A temporary ADI of 0-0.003 mg/kg of body weight was established
    for levamisole, based on a no-observed-effect level of 1.25 mg/kg
    b.w./day for the induction of haemolysis in dogs, and a safety factor
    of 500, which the Committee selected for this compound after taking
    into consideration the uncertainties regarding the relevance of the
    dog model and the fact that no threshold could be established from the
    human data.

         The Committee noted that the lowest level of levamisole reported
    to be associated with even mild neutropenia in a compromised (ill)
    human patient was at least 60 times the temporary ADI.  The Committee
    assumed that residues other than levamisole have the same potential
    toxicity as the parent drug.

         The Committee requires the following by 1994:

    1.   A comprehensive assessment of the incidence of granulocytopenia
         and agranulocytosis, thrombocytopenia and haemolytic anaemia in
         humans receiving levamisole, together with dose-response
         information.

    2.   The results of studies that demonstrate that the mechanisms for
         the production of haemolytic anaemia in dogs and neutropenia or
         agranulocytosis in humans are related phenomena, such as
         experiments in which the specificity of the antibody response and
         of the target cells is studied.

    3.   A comparison of the metabolites of levamisole produced in humans,
         laboratory animals, and food-producing animals; if differences in
         major metabolites are demonstrated, evidence should be obtained
         on the potential of the metabolites that are produced in food-
         producing animals to induce haemoatological effects.

    5.  REFERENCES

    AMERY, W., & BUTTERWORTH, B. (1983).  Review: Commentary on the Dosage
    Regimen of Levamisole in Cancer: Is it Related to Efficacy and Safety. 
     Int. J. Immunopharm., 5, 1, 1-9.

    ATWELL, R.B., THORNTON, J.R., & ODLUM, J. (1981).  Inspected Drug
    Induced Thrombocytopenia associated with Levamisole Therapy in a Dog. 
     Australian Vet., J. 57, 74-81.

    BENARD, P., BRUNET, C., CAZIN, M., BRAUN, J.P., BURGAT-SACAZE, V., &
    RICO, A.G. (1980).  Whole Body Distribution of 3H Levamisole in Rats
    and Mice.   Mechanisms of Toxicity and Hazard Evaluation.
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    BERGER, R., BERHEIM, A., FEINGOLD, J., & ANDRIEU, J.M. (1980).  The
    Effect of Levamisole on Human Chromosomes.   Path. Biol., 28, 323-
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    BOYD, J.E., BULLOCK, M.W., CHAMPAGNE, D.A., GATTERDAM, P.E., MORICI,
    I.J., PLAISTED, P.H., SPICER, L.D., WAYNE, R.S., & ZULALIAN, J.
    (1973).  Metabolism of 1-tetramisole in Rats.  Unpublished; Submitted
    to WHO by Janssen Pharmaceutica.

    COLIZZA, S., BAGOLAN, P., & DI PAOLA, M. (1981).  Side Effects to
    Levamisole Given to Neoplastic Patients as Adjuvant to Surgery: A new
    Case of Agranulocytosis.   J. Surg. Oncol., 16, 259-64.

    DAVEY, D.G. (1968a).  One Month Toxicity Test in Dogs.  Unpublished. 
    Imperial Chemical Industries Limited.  Submitted to WHO by Janssen
    Pharmaceutica.

    DAVEY, D.G. (1968b).  One Month Toxicity Test in Rats.  Unpublished. 
    Imperial Chemical Industries Limited.  Submitted to WHO by Janssen
    Pharmaceutica.

    DAVEY, D.G. (undated a).  Acute Toxicity.  Unpublished.  Imperial
    Chemical Industries Limited.  Submitted to WHO by Janssen
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    DAVEY, D.G. (undated b).  Teratogenic Test: Rabbits.  Unpublished, 
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    DAVEY, D.G. (undated c).  Teratogenic Studies.  Unpublished, Imperial
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    Pharmaceutica.

    DESPLENTER, L. (1980).  Tolerance of Levamisole Pour-on Formulation in
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    DESPLENTER, L. (1983).  Levamisole - Induced Vomiting in Dogs. 
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    DREW, S., CARTER, B., NATHANON, D., & TERASAKI, P. (1980). Levamisole-
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    ENNINGA, I.C. (1988).  Evaluation of the Ability of R12564
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    FELIX-DAVIES, (1978).  Neutropenia on Low Dosage Levamisole Therapy
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    GALTIER, P., COCHE, Y., & ALVINERIE, M. (1983).  Tissue distribution
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    Intramuscular Administration.   Xenobiotica, 13, 7, 407-413.

    GATTERDAM, P.E., CHAMPAGNE, D.A., & BOYD, J.E. (1966).  Tetramisole:
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    Excretion in Rats.  Unpublished, American Cyanamid. Submitted to WHO
    by Janssen Pharmaceutica.

    HUCHISON, E.B., MCNERY, J.,M. RIBELIN, WE., & LEVINSKAS, G.J. (1967). 
    1-Tetramisole: Ninety-Day Repeated Feeding to Dogs.  Rpt. No. 67-118. 
    Unpublished, American Cyanamid.  Submitted to WHO by Janssen
    Pharmaceutica.

    HEYKANTS, J. (1976).  Clinical Research Reports.  Original NDA.
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    IKEGAMI, J., NISHIKAWA, T., HARA,T., MIYAZAKI, E., & OHGURO, T.
    (1981).  Oral Micronucleus Test in Male Mouse.  Unpublished, Kyowa 
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    KOUASSI, E., Caille, G., Lery, L., Lariviere, L., & Vezina, M. (1986). 
    Novel Assay and Pharmacokinetics of Levamisole and P-hydroxylevamisole
    in Human Plasma and Urine.   Bio Pharm. Drug Dispos., 7, 71-89.

    MAES, L., & MARSBOOM, R. (1988).  Granulocytopenia as a Side-effect of
    Prolonged Therapy with Levamisole in Man - Is there a Relationship
    with the Wide-spread Use of Levamisole in Veterinary Medicine? 
    Unpublished; submitted to WHO by Janssen Pharmaceutica.

    MARSBOOM, R. (1969a).  Effects of Oral R12564 (levamisole) on Male and
    Female fertility.  Rpt. No. 239.  Unpublished; submitted to WHO by
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    MARSBOOM, R. (1969b).   Effects of R12546 (levamisole) in Rats After
    Oral Administration During the Peri and Postnatal Period.  Rpt. No.
    238. Unpublished; submitted to WHO by Janssen Pharmaceutica.

    MARSBOOM, R. (1972).  Potential of Oral R12564 (levamisole) for
    Embryotoxicity and Teratogenic Effects in Rats.  Rpt. No. 237. 
    Unpublished; submitted to WHO by Janssen Pharmaceutica.

    MARSBOOM, R. (1974).  Three-generation Reproduction Study in Rats with
    Oral R12546 (levamisole). Rpt. No. 537.  Unpublished; submitted to WHO
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    MARSBOOM, R. (1977).  Dominant Lethal Test in Male Mice - Single Oral
    Dose. Unpublished; submitted to WHO by Janssen Pharmaceutica.

    MARSBOOM, R., & HERIN, V. (1980).  Oral Carcinogenicity Study in
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    Pharmaceutica.

    MARSBOOM, R., HERIN, V., VANDESTEENE, R., & VAN BELLE, H. (1969).
    Thirteen Week Feeding Study of Levamisole-HCl in Rats,.  Unpublished;
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    MARSBOOM, R., VANDESTEENE, R. & PARDOEL, L. (1972).  Eighteen Month
    Feeding Study in Rats with Levamisole.  Rpt. No. 154.  Unpublished;
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    MARSBOOM, R., HERIN, V., VANDESTEENE, R. & PARDOEL, L. (1975).  Oral
    Toxicity Study in Beagle Dogs Repeated Dosage for 12 Months. 
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    MICHIELS, M., WOESTENBORGHS, R., & HEYKANTS, J. (1978).  Absorption 
    and Plasma Levels of Oral Levamisole in the Rabbit.  Unpublished;
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    NIEMEGEERS, C.M. (1975).  The Acute Intravenous, Subcutaneous, and
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    PARKINSON, D.R., JERRY, L.M., SHIBATA, H.K., LEWIS, M.G., CARO, P.O.,
    CAPEK, A., MANSELL, P.W., & MARQUIS, G. (1977).  Complications of
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    REYNTJENS. (1989).  Clinical Expert Report on Use of Levamisole for
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    RICHOLD, M. JONES, E., & PROUDLOCK, R. (1979).  Ames Metabolic
    Activation Test to Assess the Potential Mutagenic Effect of
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    THOMPSON, J., HERBICK, J., KLASSEN, C. SEVERSON, C., VELIN,V.,
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    VANDENBERGHE, J., MARSBOOM, R., & HERIN, V. (1980).  Oral
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    VAN WAUWE, J, & JANSSEN, P. (1989).  The Cardinal Question About
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    Janssen Pharmaceutica.

    VERSTRAETEN, A., HERIN, V., & MARSBOOM, R. (1983).  Subacute Toxicity
    Study in Beagle Dogs Repeated Dosage for 3 Months Pour On. 
    Unpublished; submitted to WHO by Janssen Pharmaceutica.

    VEYS, P., & DONY, J. (1985).  Embryotoxicity and Teratogenicity Study
    with Levamisole in Swine.  Unpublished; submitted to WHO by Janssen
    Pharmaceutica.

    VEYS, P. (1989).  Literature Retrieval of Reports and Publications on
    Levamisole-related Granulocytopenia.  Unpublished; submitted to WHO by
    Janssen Pharmaceutica.

    WALLWORK, L.M. & JAMES, J.A. (1975).  Rat Acute Oral and Dermal
    Toxcicity Using a "Pour-on" Formulation.  Unpublished, Wellcome
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    WANG, G.T. (1970a).  Safety study of Levamisole in Swine. 
    Unpublished, American Cyanamide.  Submitted to WHO by Janssen
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    WANG, G.T. (1970b).  Safety study of Levamisole in Swine. 
    Unpublished, American Cyanamide.  Submitted to WHO by Janssen
    Pharamaceutica.


    See Also:
       Toxicological Abbreviations
       Levamisole (WHO Food Additives Series 33)
       LEVAMISOLE (JECFA Evaluation)