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    CARAZOLOL

    First draft prepared by
    Dr. F.X.R. van Leeuwen
    Toxicology Advisory Centre
    National Institute of Public Health
    and Environmental Protection
    Bilthoven, The Netherlands

    1.  EXPLANATION

      Carazolol is a mixed -adrenoceptor blocking agent primarily used
    in pigs to prevent sudden death due to stress during transport.
    Carazolol has not been previously evaluated by the Joint FAO/WHO
    Expert Committee on Food Additives.

    2.  BIOLOGICAL DATA

    2.1  Biochemical aspects

    2.1.1  Absorption, distribution and excretion

          Groups of female Sprague-Dawley rats (10-15 weeks) were given
    0.5 mg/kg side-chain labelled 14C-carazolol intraperitoneally.
    Carazolol was determined in plasma and tissue samples after 0.25,
    0.5, 1, 2, 6, 24, and 48 hours. Peak plasma levels were observed
    after 0.25 to 1 hour and the half-life was about 24 hours. Highest
    tissue levels had been obtained by 0.25 hours in liver, kidneys and
    lungs. (Less than 0.18% was expired to air within 24 hours). After
    48 hours 93% of the dose was excreted, 45% in urine and 48% in
    faeces.

          Female non-pregnant Russian rabbits given a single oral dose of
    10 mg side-chain labelled 14C-carazolol/kg excreted 61.6% of the
    radioactivity in the urine within 24 hours (faecal excretion was not
    determined). Serum levels peaked 1 hour after dosing and the
    half-life was about 20 hours. Pregnant rabbits given 0, 10, or
    100 mg/kg orally showed the same pattern in renal excretion and
    plasma serum levels (Koch & Bartsch, 1977).

          In dogs given side-chain labelled 14C-carazolol at doses of
    5 mg/kg i.v. or 50 mg/kg orally a slow elimination with plasma
    half-lives of 30 and 20 hours, respectively, was observed. After
    intravenous administration 22% and 38% of the dose was excreted in
    the urine and faeces, respectively, within 48 hours; whereas after
    oral administration urinary excretion accounted for 13% and faecal
    excretion for 45% (Koch & Bartsch, 1977).

    2.1.2  Biotransformation

          One male beagle dog was given 10 mg side-chain labelled
    14C-carazolol (purity 96%). Urine was collected for 24 hours and
    used for metabolite investigations. Within 24 hours about 31% of the
    dose was excreted in urine. Apart from carazolol 6 metabolites were
    isolated and identified by mass spectrometry as carazolol with a
    shortened side-chain, a diastereomer pair of
    carazolol-O-glucuronides, an O-glucuronide of 6(7)-hydroxy carazolol
    and a diastereomer pair of carazolol-bis-O-glucuronide (Koch, 1977).

          Unchanged carazolol, carazolol mono-and bis-glucuronide and
    carazolol lactate were identified in the urine of pigs
    intramuscularly injected with 1 mg carazolol/100 kg b.w. Two human
    volunteers each ingested 5 mg carazolol. Urine was collected during
    the following 4.5 hours; the parent compound, carazolol
    monoglucuronide, carazolol lactate and carazolol acetate were found
    (Rudolph, 1988).

    FIGURE 1

    2.2  Toxicological studies

    2.2.1  Acute toxicity

          The acute toxicity of carazolol is given in Table 1. Deaths
    shown were recorded within the first 24 hours. The animals exhibited
    sedation, apathy, ventral position, slowed respiration and
    convulsions shortly before death.

        Table 1: The acute toxicity of carazolol
                                                                                  

    Species        Route         Sex          LD50 (mg/kg b.w.)    Reference
                                                                                  

    Mouse          oral          M            1321                 Czerwek, 1978
                                 F            1601
                   i.p.          M             561
                                 F             621
                   i.v.          M&F           142

    Rat            oral          M             881
                                 F             801
                   i.p.          M             621
                                 F             591
                   i.v.          M&F           10.43

    Rabbit         i.v.          M&F           5.24
                                                                                  

    1.   vehicle: tylose
    2.   vehicle: Dimethylformamide (DMF) in glucose
    3.   vehicle: trisodium citrate, citric acid and polyethylene glycol
         in water
    4.   vehicle: DMF in NaCl
    
    2.2.2  Short-term studies

    2.2.2.1  Rats

          Groups of Sprague-Dawley rats (10/sex/group) were fed a diet
    containing 0, 20, 70, or 200 mg/kg carazolol for 14 days. No
    dose-related effects were observed on clinical signs, body weight,
    food intake, food efficiency, haematology, clinical chemistry,
    urinalysis, organ weight, macroscopy or histopathology. The NOAEL in
    this study was 200 mg carazolol/kg food, equal to 18.9 and
    18.3 mg/kg b.w. for males and females, respectively (Rebel et al.,
    1974a).

          Groups of Sprague-Dawley rats (10/sex/group) were given i.p.
    injections once daily of 0, 1.0, 3.0, or 9.0 mg carazolol/kg b.w.
    for 4 weeks. No treatment-related effects were observed on clinical
    signs, body weight, food consumption, haematology, clinical
    chemistry, urinalysis, macroscopy, or histopathology. The NOAEL in
    this study was 9 mg/kg b.w. (Rebel et al., 1975a).

          Groups of Sprague-Dawley rats (20/sex/group) were administered
    0, 40, 120, or 400 mg carazolol/kg food (equal to 0, 2.7 and 3.2,
    8.2 and 9.5, or 27.3 and 30.4 mg/kg b.w./day for males and females,
    respectively) in the diet for 3 months. Rats (5/sex) of the control
    and highest dose group were given a 4-week recovery period.
    High-dose females exhibited a decreased body weight gain due to a
    lower food intake from week 5 onwards. They had completely recovered
    from this effect after 4 weeks. A significantly lower heart rate in
    conscious rats was observed in all treated animals (males and
    females combined), without any dose-response relationship. The
    latter might be due to a (sub)maximal pharmacological dose. However,
    interpretation of the results is hampered by a pre-existing
    difference in initial heart rate between rats allocated to the
    control and the treatment groups. No treatment-related effect was
    observed on clinical signs, haematology, clinical chemistry,
    urinalysis, organ weight, macroscopy or histopathology (Rebel
    et al., 1976a).

          Groups of Sprague-Dawley rats (30/sex/group) were fed a diet
    containing 0, 150, 300, or 600-1800 mg carazolol/kg food (equal to 7
    and 9, 14, and 17, or 33 - 69 and 36 - 86 mg/kg b.w./day for males
    and females, respectively) for 12 months. The concentration of
    carazolol in diet of the highest dose group was 600 mg/kg up to week
    22, 1200 mg/kg from week 22 to week 40, and 1800 mg/kg from week 40
    to the end of the experiment. Five male and 5 female rats per group
    were given a 4-week recovery period at the end of the experiment.
    Male as well as female rats at the highest dose group showed a rough
    pelt on increasing the dose to 1200 mg/kg. High-dose rats showed a
    decreased food intake (from week 40) and a decrease in body weight
    gain from week 28 in males and from week 33 in females. At recovery
    a higher food consumption was observed in the same dose group; in
    males delayed body weight gain was reversible. In male as well as in
    female rats relative heart weight showed a significant but not
    dose-related increase at all dose levels. Relative kidney, ovary and
    testes weights were increased in rats at the highest dose. No
    treatment-related effects were observed on haematology, clinical
    chemistry, urinalysis, macroscopy and microscopy (Hebold et al.,
    1978a).

    2.2.2.2.  Dogs

          Groups of beagle dogs (2/sex/group) were administered 0, 1, 3,
    or 10 mg carazolol/kg b.w./day for 14 days. Observations included
    clinical signs, body weight, food consumption, haematology, clinical
    chemistry, urinalysis, heart rate, BSP retention, neurological
    investigations, organ weight, macroscopy, and histopathology.
    Treatment-related effects observed in high-dose females consisted of
    decreased food consumption and body weight, decrease in Hb, Ht and
    erythrocytes, a marked acceleration of the erythrocyte sedimentation
    rate, an increase in glucose, cholesterol, AP and ALAT. At
    histopathology, accumulation of mesenchyme cells was seen in one
    high-dose female, the other one showed an increased activation of
    Kupffer's cells. The NOAEL in this study was 3 mg/kg b.w./day (Rebel
    et al., 1974b).

          Groups of beagle dogs (2/sex/group) were given i.v. injections
    once daily of 0, 0.5, 1.5, or 4.5 mg carazolol/kg b.w. for 4 weeks.
    No treatment-related effects were observed on clinical signs, body
    weight, food consumption, heart rate, neurological investigations,
    haematology, clinical chemistry, urinalysis, organ weight,
    macroscopy and histopathology (Rebel et al., 1975b).

          Groups of beagle dogs (3/sex/group, 13 months old) were given
    0, 2, 6, or 20 mg/kg b.w. carazolol in 2 daily doses for 3 months.
    One male and one female dog from the control group and the high-dose
    group remained on a 4-week recovery period. Observations included
    clinical signs, food intake, body weight, heart rate, neurological
    investigations, haematology, clinical chemistry, urinalysis, organ
    weights, macroscopy and histopathology. High-dose females exhibited
    an increase in erythrocyte sedimentation rate, AP and ALAT activity
    and cholesterol concentration (Rebel et al., 1976b).

          Groups of beagle dogs (5/sex/group) were administered 2 daily
    doses of 0, 7, 15, or 30 (week 1-18) and 60 (week 18-52) mg
    carazolol/kg b.w. for 12 months. Two male and 2 female dogs were
    observed during a subsequent 5-week recovery period. No effects were
    observed on clinical signs, food consumption, body weight, heart
    rate, neurological investigations, haematology, clinical chemistry,
    urinalysis, macroscopy, or microscopy. An increase in relative
    weight of liver, kidney, and testes was apparent in male dogs at the
    highest dose. The NOEL in this study was 15 mg/kg b.w. twice daily
    (Hebold, et al., 1978b). Remark: no statistics were performed.

    2.2.3  Long-term carcinogenicity study

    2.2.3.1  Rats

          Groups of Sprague-Dawley rats (72/sex/group) received a diet
    containing 0, 100, 300, or 900 mg/kg food for 26 months.
    Observations included clinical signs, food consumption, body weight,
    haematology, clinical chemistry, macroscopy and microscopy. Survival
    was increased in dosed rats (48/72 and 41/72, 44/72 and 47/72, 51/72
    and 53/72, and 60/72 and 57/72 for males and females at 0, 100, 300,
    and 900 ppm, respectively). A treatment-related significant decrease
    in body weight gain was observed at 300 and 900 mg/kg in both sexes
    and at 100 mg/kg food in female rats. Food consumption was
    significantly decreased in high-dose male and female rats and in
    females at 300 mg/kg from day 464 onwards. A decrease in neutrophils
    and eosinophils (males only) was observed at 300 and 900 mg/kg food.
    At the same dose levels glucose and protein levels were decreased in
    both males and females. At 900 mg/kg food glucose was decreased in
    females and creatinine in males. The incidence of all tumours
    combined was not enhanced (Hartig, 1981). Remark: only summarized
    data were available.

    2.2.4  Reproduction studies

    2.2.4.1  Rats

          Male rats were administered diets containing 0, 40, or
    400 mg/kg food mg carazolol/kg food for 10 weeks. Rats were then
    allowed to mate with untreated females. The newly-born were counted
    and weighed. Body weight was slightly decreased in high-dosed males.
    No treatment-related effects were observed on indices for fertility,
    gestation, viability and lactation. No difference in offspring born
    alive or dead, number of live fetuses, fetal weight or behaviour of
    the offspring was observed. At 21 days of age the offspring were
    killed and no malformations were observed (Hebold & Czerwek, 1978).
    Remark: summary only available.

          In a 3-generation reproduction study with a teratology phase
    (see Special studies on embryotoxicity and teratogenicity, Section
    2.2.5.1) female Sprague-Dawley rats (76/group) were orally
    administered by gavage 0, 15, 30, or 60 mg/kg b.w./day carazolol
    suspended in methyl cellulose. Administration started from 14 days
    before the first mating with untreated males (for all females/group)
    throughout the entire pregnancy (22-27 pregnant rats/group) until
    day 21 of lactation. Eleven-12 dams/group were killed on day 21 of
    pregnancy and their fetuses were delivered by caesarian section.
    F1 animals (1/sex/litter) were mated and gave birth to the F2
    generation. During the 14-day premating period a slight sedation was
    observed from days 3-6 at the highest dose and a significantly
    increased body weight as well as body weight gain were observed at

    30 and 60 mg/kg b.w./day. No effects were observed on the fertility
    index. At 60 mg/kg b.w./day the rearing performance of the F0
    animals during the lactation period was impaired. At 60 mg/kg b.w.
    post-implantation loss was significantly increased in the F0 dams
    and the number of F1 pups alive at the end of the lactation period
    was significantly decreased. At the highest dose a significantly
    lower pup weight was observed in the F1 generation shortly after
    delivery. At 30 and 60 mg/kg b.w./day post-implantation loss was
    significantly increased in F1 dams and a significant decrease was
    observed in the number of F2 young alive on the day after birth.
    The NOAEL in this study was 15 mg carazolol/kg b.w./day (Sterz &
    Vollmar, 1978).

    2.2.5  Special studies on embryotoxicity and teratogenicity

    2.2.5.1  Rats

          Groups of 24 pregnant Sprague-Dawley rats were administered 0,
    25, 50, or 100 mg carazolol/kg b.w/day from days 6-15 of pregnancy
    by gavage. Dams were killed on gestation day 19. Observations
    included clinical signs, condition of faeces, food and drinking
    water consumption, and body weight. On day 19 of gestation the
    females were sacrificed and the uteri and ovaries were examined.
    Other organs were macroscopally examined. Fetuses were weighed,
    sexed, and examined for external, visceral, and skeletal
    malformations. Maternal toxicity (ataxia and sedation) was observed
    at 50 mg carazolol/kg b.w./day, and more marked at 100 mg/kg
    b.w./day. At the highest dose an increase in post-implantation loss
    was observed. There was no evidence of embryotoxicity or
    irreversible structural effects (Leuschner, 1975).

          A teratological examination was conducted during the course of
    the 2-generation rat reproduction study (see Reproduction studies,
    Section 2.2.4). No effects were observed on number of corpora lutea,
    number of implantations, pre-implantation loss, resorptions, live
    and dead fetuses, fetal weight, sex ratio, or external, visceral,
    and skeletal malformations. From days 1-22 of pregnancy high-dose
    dams exhibited a reduced body weight gain. Placental weight was
    significantly increased at 30 and 60 mg/kg b.w./day (not
    dose-related). A decrease in number of ossified cervical vertebrae
    or tail vertebrae was observed in the mid- and high-dose groups. No
    irreversible structural effects were observed (Sterz & Vollmar,
    1978).

    2.2.5.2  Rabbits

          Groups of 17 pregnant Himalayan rabbits were orally
    administered 0, 25, 50, or 100 mg carazolol/kg b.w/day from days
    7-19 of gestation. The females were killed on gestation day 31 and

    fetuses were delivered by caesarean section. During the
    administration period food consumption was reduced in all groups,
    significantly at 100 mg/kg b.w./day; a significant increase in food
    consumption was observed in high-dose females the last 6 days of the
    test. Weight gain of dams at the highest dose was significantly
    increased from days 20 to 31 of pregnancy. Independent of the
    dosage, 3 cases of arthrogryposis occurred in 30 litters (0, 1, 1,
    and 1 at 0, 25, 50 and 100 mg/kg b.w./day, respectively). No
    treatment-related effects were observed in number of corpora lutea,
    implantation loss, resorptions, litter size, live and dead fetuses,
    fetal weight, sex ratio, or internal and skeletal malformations
    (Sterz & Glocke, 1977a).

          Groups of pregnant Himalayan rabbits (13-14/group) received
    orally 0, 6.26, 12.50, or 100 mg carazolol/kg b.w./day from days
    7-19 of gestation. The females were killed on day 31 of gestation
    and the fetuses were delivered by caesarean section. Food
    consumption was decreased at the highest dose. In the mid-dose
    group, one dead and one underdeveloped fetus were seen. In the
    high-dose group, one dead and two underdeveloped fetuses were seen.
    Placental weight was significantly decreased at the highest dose and
    fetal weight was significantly and dose-relatedly decreased at 12.50
    and 100 mg/kg b.w./day. One fetus with pin-head size meningocele on
    the occiput was observed at 100 mg/kg b.w./day. Arthrogryposis was
    observed in 0, 1, 1, and 1 fetus at 0, 6.25, 12.50, and 100 mg/kg
    b.w./day, respectively. One fetus with spondylosis syndrome and one
    fetus with scoliosis due to reduction and absence of parts of the
    first two lumbar vertebrae were observed at the mid- and high-dose,
    respectively. No treatment-related effects were observed on
    fertility index, body weight, number of corpora lutea, implantation
    loss, resorptions, litter size, or sex ratio (Sterz & Glocke,
    1977b).

          A third experiment (using the same experimental design) was
    carried out in which particular attention was directed towards any
    occurrence of deformities of the limbs (arthrogryposis). Twenty-nine
    and 20 Himalayan pregnant rabbits were orally administered 0 and
    100 mg carazolol/kg b.w./day from days 9-12 of gestation,
    respectively. No treatment-related effects were observed on food
    consumption or body weight (only recorded in 10 control and 4
    experimental rabbits) or reproduction performance. No abnormalities
    were observed after skeletal and visceral examinations, except for a
    significantly increased number of extra ribs at the 1st lumbar
    vertebra. The authors concluded that the observed cases of
    arthrogrypsosis in the previous reported studies were in fact a
    fortuitous increase in incidence of this spontaneous deformity of
    the rabbits strain used (Sterz & Glocke, 1977c).

    2.2.6  Special studies on pharmacology

    2.2.6.1  Mice

          Groups of female SPF mice fasted for 18 hours were given i.p.
    doses of 0, 20, or 200 mg carazolol/kg b.w. or 200 mg propranolol/kg
    b.w. Intestinal motility was significantly increased after both
    carazolol and propranolol administration (Roesch, 1978). Barbiturate
    sleep in groups of mice given s.c. 8, 16, 32, or 64 mg carazolol/kg
    b.w. was not affected at doses < 16 mg/kg b.w.; all mice died at
    64 mg/kg b.w. Induced fighting behaviour was dose-dependently
    inhibited in mice given 0, 2, 4, 8 or 16 mg carazolol s.c./kg b.w.
    at doses of 4-16 mg/kg. Electroshock-induced convulsions were
    inhibited in 1/10 mice and 10/10 mice at 16 and 32 mg carazolol/kg
    b.w., respectively. Metrazole-induced convulsions were
    dose-dependently inhibited in mice given 4-32 mg carazolol/kg b.w.
    In a traction test with mice the ability to cling to the wire was
    blocked in 0/10, 1/10, and 10/10 mice at 8, 16, and 32 mg
    carazolol/kg b.w., respectively (Kumada & Ohtsuka, 1978).

    2.2.6.1  Rats

          No indication of an effect on the central nervous system was
    observed in male Sprague-Dawley rats given intraperitoneally
    10 mg/kg b.w. carazolol (Roesch, 1973). No effects were observed on
    the urine and electrolyte excretion in female SPF-Sprague-Dawley
    rats after the oral or i.p. administration of 10 mg/kg b.w.
    carazolol (Bartsch, 1974a).

    2.2.6.3  Rabbits

          1 mg carazolol/kg b.w. administered intravenously to conscious
    rabbits did not cause an effect on body temperature; blood glucose
    levels were slightly increased at this dose (Hebold, 1974).
    Carazolol given at doses of 50 mg/kg b.w. orally, or at 5 or
    10 mg/kg b.w i.v. to male and female mixed-breed rabbits inhibited
    an isoprenaline-induced tachycardia; at 20 mg/kg b.w. orally no
    inhibition was found. A dose of 5 mg carazolol/kg b.w. intravenously
    administered to conscious rabbits inhibited isoprenaline-induced
    tachycardia (Bartsch 1974b).

    2.2.6.4  Dogs

          No effects were observed on the urine and electrolyte excretion
    in female beagle dogs given 5 mg carazolol/kg b.w. orally (Bartsch,
    1974). Conscious dogs were intravenously administered 0.5, 1.0, 2.0,
    or 5.0 mg carazolol/kg b.w. over a period of 15 seconds. At 1.0 and
    2.0 mg/kg b.w. heart rate was increased without affecting the PQ

    interval, but with slight changes in the ECG. At these doses the
    behaviour of the dogs was normal. At the highest dose of 5.0 mg/kg
    vomiting, tachypnoea, tachycardia and changes in the PQ-section of
    the ECG were observed (Bartsch, 1977).

          One, 10, or 100 mg carazolol/kg b.w. given i.v. to
    anaesthetized mongrel dogs antagonized isoprenaline-induced
    responses. In another experiment, 0.01, 0.1, 1.0, or 10 mg
    carazolol/kg b.w. was intravenously given to anaesthetized mongrel
    dogs. At doses of 1.0 mg/kg b.w. and higher, depressive effects on
    the cardiovascular system which included decreases in ABP (arterial
    blood pressure), LVP (left ventricular pressure) and dp/dt (cardiac
    output), and an increase of IVEDP (left ventricular end diastolic
    pressure) were observed (Satoh et al., 1980).

          One, 4, 16, or 64 mg carazolol/kg b.w. was intravenously given
    to mongrel dogs. A dose-dependent inhibition of
    isoproterenol-induced tachycardia as well as isoprenaline-induced
    increase of cardiac output was observed; at the highest dose an
    almost complete blockade was observed. In mongrel dogs a
    dose-dependent inhibition of tachycardia as well as increase in
    cardiac output induced by sympathetic nerve stimulation was also
    observed after the i.v. administration of 0.25 to 16 mg carazolol/kg
    b.w. (Kumada & Ohtsuka, 1978).

    2.2.7  Special studies on genotoxicity

        Table 2: Results of genotoxicity assays on carazolol
                                                                                               

    Test system       Test object            Concentration              Result       Reference
                                                                                               

    In vitro          S. typhimurium         0-5000 mg/pl1              negative     Grafe, 1978
    Ames test         TA98, TA100            in DMF mg/pl1
                      TA1535, TA1537
                      TA1538

    In vivo           male NMRI              single oral dose           negative     Grafe &
    Dominant          mice                   of 20 or 80 mg/kg b.w.                  Vollmar,
    lethal assay                             or 13.5 mg/kg b.w.                      1976
                                             single i.p. dose

    Dominant          female NMRI            single oral dose           negative     Grafe &
    lethal assay      Kisslegg mice          of 50 mg/kg b.w. or                     Vollmar,
                                             13.5 mg/kg b.w. single                  1976
                                             i.p. dose

    Host-mediated     NMRI/Kisslegg          80 mg/kg b.w. oral or      negative     Grafe &
    assay             mice with              13.6 mg/kg b.w. s.c.                    Vollmar,
                      S. typhimurium                                                 1976
                      G46 S. marcescens

    Cytogenicity      Chinese hamster        2 x 400 mg/kg b.w.         negative     Grafe &
    assay                                    oral or 1 x 20 mg/kg                    Vollmar,
    (spermatogonia                           b.w. i.p. or 3 x weekly                 1976
    as well as                               for 13 weeks a
    bone marrow)2                            treatment with 20 mg/kg
                                             b.w. oral or 1 mg/kg
                                             b.w. i.p.; all suspended
                                             in CMC
                                                                                               

    1.   both with and without rat liver S-9 fraction
    2.   only a negative control group (compound not indicated) was tested
    

    2.3  Observations in humans

          Twelve healthy male volunteers were given carazolol in a 3-way
    crossover experiment at doses of 0.5 mg i.v., 5.0 mg oral or 7.5 mg
    oral. Ergometric tests were carried out before and 1, 2, 3, 4, 8,
    12, and 16 hours after carazolol administration. The subjects laid

    down for about 20 minutes before each test. The heart rate, blood
    pressure, the pressure-rate product, and the relative enteral
    efficacy were determined. Heart rate was maximally inhibited by
    1-2 hours after administration (15%, 13%, and 15% at 0.5 mg i.v.;
    5.0 and 7.5 mg oral, respectively). During exercise the systolic
    blood pressure was lowered by a maximum of 12% (oral dose) or 15%
    (i.v. dose) at 1 hour. The maximal reduction of the pressure rate
    product was 28%, 26%, and 25% at 0.5 mg i.v., 5.0 and 7.5 mg oral,
    respectively. The mean duration of action of an oral dose of 5 mg
    was estimated as 10 hours. The relative enteral efficacy calculated
    by comparison of the inhibitory areas after both oral doses with
    those of an i.v. dose did not differ significantly and was about
    10%. By using the dose-reponse curve the authors extrapolated a
    no-effect dose for the oral route of 10 mg/kg b.w. (Mollendorff
    et al., 1979).

          In a cross-over experiment 8 patients with chronic bronchitis
    and partial reversibility of the obstruction were given a placebo or
    carazolol randomly. Two patients received both 0.1 and 0.7 mg
    carazolol, while the other 6 received either 0.1 or 0.7 mg. Vital
    capacity (VC) and forced expiratory volume (FEV) were measured
    before and 1, 2, and 3 hours after administration of the substances.
    No statistics were carried out. At 0.7 mg carazolol a definite
    increase in bronchial resistance was observed and dyspnoea was seen
    in 3/5 patients leading to discontinuation of the test. At 0.1 mg
    carazolol, the tests did not have to be discontinued in any of the
    patients; only one patient showed slight dyspnoea with a decrease in
    FEV . The author estimated that a dose of 0.03 mg carazolol no
    longer induces any effect on the bronchial system (Huckauf,
    undated).

    3.  COMMENTS

          The Committee considered pharmacological and toxicological data
    from pharmacodynamic, pharmacokinetic, metabolism, acute and
    short-term toxicity, carcinogenicity, genotoxicity, reproduction and
    teratology studies, as well as the results of clinical trials in
    humans.

          The distribution, excretion and biotransformation of
    radiolabelled carazolol were studied in rats, rabbits and dogs.
    After oral ingestion, carazolol was rapidly absorbed. In rats, the
    radioactivity was widely distributed in the tissues, with the
    highest levels in liver, kidneys, and lungs. Excretion was almost
    complete within 48 hours, equally divided between the urine and
    faeces. In rabbits, peak plasma levels were reached 1 hour after a
    single oral dose of 10 mg/kg b.w., and about 60% of the dose was
    excreted in urine. Following oral administration of carazolol in
    dogs, 13% of the radioactivity was excreted in urine and 45% in
    faeces within 48 hours. In the urine of a dog given 10 mg of [14C]
    carazolol/kg body weight intravenously, the parent compound and six
    metabolites were identified. Both carazolol and its glucuronide,
    lactate, and acetate metabolites have been identified in the urine
    of pigs and humans.

          In a short-term study in rats, in which carazolol was
    administered in the diet at levels up to 400 mg/kg of feed for 13
    weeks, females exhibited a decrease in both body weight and food
    intake at the highest dose. Heart rate was decreased even at the
    lowest dose of 40 mg/kg of feed. When rats received carazolol in the
    feed for 1 year a decrease in body weight due to decreased food
    intake at the highest dose level was observed in both males and
    females only after progessively increasing this dose to 1200 and
    subsequently to 1800 mg/kg of feed. A statistically significant
    increase in relative heart weight was observed in rats at all dose
    levels, but this was not dose related.

          In short-term studies in dogs dosed orally at up to 20 mg kg
    b.w./day, blood chemistry and histopathological changes provided
    evidence of hepatoxicity. The NOEL was 3 mg/kg b.w./day. In a 1-year
    study, changes in relative organ weights (liver, kidney and testes)
    were observed at the dose of 30-60 mg/kg b.w./day, with a NOEL of
    15 mg/kg b.w./day.

          In a long-term study with rats at dose levels of 100, 300 and
    900 mg/kg of feed, body weight gain was reduced, even at the lowest
    dose level in females, and haematological and biochemical changes
    were found at the two highest dose levels. No increase in tumour
    incidence was observed.

          In teratogenicity studies in rats, no malformations were
    observed at doses of up to 100 mg/kg b.w./day but embryotoxicity and
    maternal toxicity were observed at doses of 30 mg/kg b.w./day and
    above. The NOEL was 15 mg/kg b.w./day In one of three teratogenicity
    studies in rabbits, one fetus with structural malformations was
    observed in the mid-dose group and one in the high dose group,
    giving a NOEL of 6.25 mg/kg b.w./day.

          In a two-generation reproduction study in rats, in which
    carazolol was administered by gavage at doses of up to 60 mg/kg
    b.w./day, an increase in post implantation losses, and a decrease in
    the number of live pups in the first and second generations were
    observed in both the mid- and the high-dose groups. The NOEL in this
    study was 15 mg/kg b.w./day.

          Carazolol gave negative results in five  in vitro and  in vivo
    genotoxicity tests.

          The -adrenoceptor-blocking activity of carazolol was
    established in specific function tests in mice, rats, rabbits, and
    dogs. A NOEL of 0.02 mg/kg b.w. for the inhibition of
    isoprenaline-induced tachycardia was observed in rabbits after
    administration of a single oral dose.

          In a clinical trial with healthy human volunteers, the effect
    on cardiac function was determined following administration of a
    single oral dose of 5 or 7 mg of carazolol/person. From the
    dose-response curve, a dose without effect of about 0.01 mg/kg b.w.
    was extrapolated. Patients suffering from chronic bronchitis showed
    a clear effect on respiratory function after a single oral dose of
    0.7 mg/person and a marginal effect at a dose of 0.1 mg/person.
    Based on these results, a NOEL of about 0.03 mg/person, equivalent
    to 0.5 g/kg b.w., was extrapolated, but the Committee noted that no
    information was provided about the procedures used in these
    extrapolations.

    4.  EVALUATION

          The Committee noted that most of the toxicological data were
    available only in summary form and that only one long-term toxicity/
    carcinogenicity study was available. Since the NOEL of 3 mg/kg
    b.w./day, observed in short-term toxicity studies in dogs, was
    several orders of magnitude higher than the NOELs for carazolol in
    pharmacological function studies, the Committee concluded that the
    pharmacological effect provided a more appropriate basis for the
    safety evaluation of residues. Because the information required to
    extrapolate to a dose without effect was lacking in the human
    studies, the Committee was not able to derive a clear NOEL for
    humans that would also cover specific groups who might be at risk,
    such as people suffering from cardiac or respiratory disease,
    particularly asthma. A temporary ADI of 0-0.1 g/kg b.w. was
    therefore established, based on a NOEL of 0.02 mg/kg b.w. for the
    inhibition of isoprenaline-induced tachycardia in rabbits and the
    application of a conventional safety factor of 200 for a temporary
    ADI based on animal studies. The Committee noted that, if the
    pharmacological NOELs extrapolated from the human studies were used,
    an ADI of a similar order of magnitude would be obtained.

    5.  REFERENCES

    BARTSCH, W. (1974a) General pharmacology of BM 51.052. Unpublished
    Reports E 2, E 4, dated 2-1974 from Boehringer, pharmakologisches
    labor, Mannheim. Submitted to WHO by Praemix Wirkstoff GMBH,
    Mannheim.

    BARTSCH, W. (1974b) Special pharmacology of BM 51.052. Unpublished
    Reports D1, D2, D4, dated 3-1974 from Boehringer, pharmakologisches
    labor, Mannheim. Submitted to WHO by Praemix Wirkstoff GMBH,
    Mannheim.

    BARTSCH, W. (1977) Tolerance testing on intravenous administration
    of high doses of BM 51.052 in conscious dogs. Unpublished Report No.
    E 6 dated 22-11-1977 from Boehringer, Mannheim. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    BARTSCH, W. (1978) Special pharmacology of BM 51.052. Unpublished
    Reports D3 and D5 dated 7-1978 from Boehringer, Mannheim. Submitted
    to WHO by Praemix Wirkstoff GMBH, Mannheim.

    CZERWEK, H. (1978) Akute toxizitat BM 51.052. Unpublished Report
    dated 1-9-1978 from Boehringer, Abt. fur Toxicologie, Mannheim.
    Submitted to WHO by Praemix Wirkstoff GMBH, Mannheim.

    GRAFE (1978) Mutagenicity BM 51.052 Ames-test. Unpublished Report
    dated 23-10-1978 from Department of Genetics, Boehringer Mannheim
    GMBH. Submitted to WHO by Praemix Wirkstoff GMBH, Mannheim.

    GRAFE & VOLLMAR, J. (1976) Mutagenicity BM 51.052. Unpublished
    Report dated 30-03-1976 from Abteilung fur Genetik, Boehringer
    Mannheim GMBH. Submitted to WHO by Praemix Wirkstoff GMBH, Mannheim.

    HARTIG, F. (1981) Chronic oral carcinogenicity test of BM 51.052,
    2-year experiment in rats. Unpublished Report 1-12/16/8/D-E/DrH/btza
    dated 25-11-1981 submitted to WHO by Praemix Wirkstoff GMBH,
    Mannheim.

    HEBOLD, G. (1974) Effect of BM 51.052 on the body temperature and
    blood sugar of conscious rabbits. Unpublished Report E 5 dated
    11-2-1974 from Boehringer, Mannheim. Submitted to WHO by Praemix
    Wirkstoff GMBH, Mannheim.

    HEBOLD, G., BLEUEL, H., CZERWEK, H., HARTIG, F. & TEUTE, H.W.
    (1978a) Chronic oral toxicity test of BM 51.052 12 months'
    experiment in rats. Unpublished Report 9-2/07/11/D-E/DrH/btza dated
    23-06-1978 from Boehringer Mannheim GmbH. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    HEBOLD, G., BLEUEL, H., CZERWEK, H., HARTIG, F. & TEUTE, H.W.
    (1978b) Pathology and toxicology BM 51.052 1 year experiment in
    dogs. Unpublished Report no. DrH/elm 8-8/31/2 dated 19-7-1978 from
    Boehringer Mannheim GMBH. Submitted to WHO by Praemix Wirkstoff
    GMBH, Mannheim.

    HEBOLD, G. & CZERWEK, H. (1978) Fertility tests on male rats given
    BM 51.052. Unpublished report dated 2-08-1978 from Boehringer
    Mannheim GmbH. Submitted to WHO by Praemix Wirkstoff GMBH, Mannheim.

    HUCKAUF, H. (undated) Clinical trial of carazolol to determine a
    threshold dose on the bronchial system. Report from Medizinische
    Klinik und Poliklinik, Klinikum Steglitz, Freie Universitat Berlin.
    Submitted to WHO by Praemix Wirkstoff GMBH, Mannheim.

    KOCH, K. (1977) Metabolism of BM 51.052. Unpublished report dated
    09-08-1977 from Boehringer, Mannheim. Submitted to WHO by Praemix
    Wirkstoff GMBH, Mannheim.

    KOCH, K. & BARTSCH, W. (1977) Investigations on the pharmacokinetics
    of BM 51.052 (carazolol). Unpublished report dated 20-02-1977 from
    Boehringer, Mannheim. Submitted to WHO by Praemix Wirkstoff GMBH,
    Mannheim.

    LEUSCHNER, F. (1975) The effect of BM 51.052 (micronized), Batch no
    807035 A on the pregnant rat and foetus on administration by gavage.
    Unpublished report dated 18-11-1975 from Mannheim Boehringer,
    laboratorium fur farmakologie und toxicologie. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    MOLLENDORF, E.v., GLOCKE, M.H. & ABSHAGEN, U. (1979) Effect kinetics
    of carazolol (BM 510952). Unpublished Report M5-01-78 dated
    17-10-1979 from Department of Clinical Pharmacology, Boehringer,
    Mannheim. Submitted to WHO by Praemix Wirkstoff GMBH, Mannheim.

    REBEL, CZERWEK, H., HARTIG, F. & TEUTE, H.W. (1974a) Pathology and
    toxicology BM 51.052 14 day experiment in rats. Unpublished Report
    7-1/1-/2 dated 26-7-1974 from Boehringer Mannheim GmbH, Abteilung
    fur experimentelle pathologie und toxikologie. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    REBEL, CZERWEK, H., HARTIG, F. & TEUTE, H.W. (1974b) Pathology and
    toxicology BM 51.052 14-day experiment in dogs. Unpublished Report
    7-1/11/1 dated 16-8-1974 from Boehringer Mannheim GmbH, Abteilung
    fur experimentelle pathologie und toxikologie. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    REBEL, CZERWEK, H., HARTIG, F. & TEUTE, H.W. (1975a) Pathology and
    toxicology BM 51.052 4 week experiment in rats. Unpublished Report
    6-12/15/2 dated 2-10-1975 from Boehringer Mannheim GmbH, Abteilung
    fur experimentelle pathologie und toxikologie. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    REBEL, CZERWEK, H., HARTIG, F. & TEUTE, H.W. (1975b) Pathology and
    toxicology BM 51.052 4 week experiment in dogs. Unpublished Report
    6-12/21/1 dated 31-10-1975 from Boehringer Mannheim GmbH, Abteilung
    fur experimentelle pathologie und toxicologie. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    REBEL, CZERWEK, H., HARTIG, F. & TEUTE, H.W. (1976a) Pathology and
    Toxicology BM 51.052 3 month experiment in rats. Unpublished Report
    6-12/27/2 dated 28-1-1976 from Boehringer Mannheim GmbH. Abteilung
    fur experimentelle pathologie und toxicologie. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    REBEL, CZERWEK, H., HARTIG, F. & TEUTE, H.W. (1976b) Pathology and
    toxicology BM 51.052 3 month experiment in dogs. Unpublished Report
    6-12/27/1 dated 2-2-1976 from Boehringer Mannheim GmbH. Abteilung
    fur experimentelle pathologie und toxicologie. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    ROESCH, A, (1973) Investigation of the action of BM 51.052 on the
    central nervous system of the rat. Unpublished Report E.1 dated
    21-08-1973 from Boehringer, Mannheim. Submitted to WHO by Praemix
    Wirkstoff GMBH, Mannheim.

    ROESCH, A. (1978) Transport function of the intestines-mouse.
    Unpublished Report E 3 dated 26-06-1978 from Boehringer, Mannheim.
    Submitted to WHO by Praemix Wirkstodd GMBH, Mannheim.

    SATOH, H., MIURA, Y., INUI, J. & HASEGAWA, G. (1980) -adrenoceptor
    blocking, cardiovascular and electrophysiological effects of
    carazolol. Unpublished report from research laboratories, Yoshitomi
    Pharmaceutical Industry Ltd. Submitted to WHO by Praemix Wirkstoff
    GMBH, Mannheim.

    STERZ, H. & GLOCKE, M.H. (1977a) Teratological investigations with
    BM 51052 in rabbits. Unpublished Report K2A dated 18-03-1977 from
    Boehringer Mannheim GMBH, teratology department. Submitted to WHO by
    Praemix Wirkstoff GMBH, Mannheim.

    STERZ, H. & GLOCKE, M.H. (1977b) Teratological investigations with
    BM 51.052 in rabbits (1st repeat and extension). Unpublished Report
    K2B dated 18-03-1977 from Boehringer Mannheim GMBH, teratological
    department. Submitted to WHO by Praemix Wirkstoff GMBH, Mannheim.

    STERZ, H. & GLOCKE, M.H. (1977c) Teratological investigations with
    BM 51052 in rabbits (2nd repeat). Unpublished Report K2C dated
    18-03-1977 from Boehringer Mannheim GMBH, Teratological Department.
    Submitted to WHO by Praemix Wirkstoff GMBH, Mannheim.

    STERZ, H. & VOLLMAR, J. (1978) Reproduction toxicology
    investigations phase I (Fertility) in female rats using BM 51.052
    p.o. Unpublished Report K4 from Department of Reproduction
    Toxicology/General Biometry, Boehringer Mannheim GmbH. Submitted to
    WHO by Praemix Wirkstoff GMBH, Mannheim.


    See Also:
       Toxicological Abbreviations
       Carazolol (WHO Food Additives Series 34)
       CARAZOLOL (JECFA Evaluation)