International Agency for Research on Cancer (IARC) - Summaries & Evaluations
4,5',8-TRIMETHYLPSORALEN
VOL.: 40 (1986) (p. 357)
5. Summary of Data Reported and Evaluation
5.1 Exposure
4,5',8-Trimethylpsoralen (trioxsalen) has been used in conjunction
with ultraviolet A radiation in the treatment of vitiligo, psoriasis
and other skin disorders. Human exposure occurs through the oral
administration or skin application of these products.
5.2 Experimental data
In one incompletely reported study of the skin carcinogenicity of
4,5',8-trimethylpsoralen in combination with ultraviolet A radiation
in mice, no skin tumour was described. No data were available to
evaluate the carcinogenicity to experimental animals of
4,5',8-trimethylpsoralen in the absence of ultraviolet A radiation.
No data were available to evaluate the reproductive effects or
prenatal toxicity of 4,5',8-trimethylpsoralen to experimental animals.
In the presence of ultraviolet A radiation, 4,5',8-trimethylpsoralen
bound covalently to isolated DNA and to DNA in bacteria, yeast and
mammalian cells in culture, and in guinea-pig skin in vivo. It induced
DNA damage in bacteria in the dark. In combination with ultraviolet A
radiation, it induced mutation in bacteriophage. The compound was
mutagenic to bacteria in the dark and with ultraviolet A radiation,
and to yeast in the presence of ultraviolet A radiation.
4,5',8-Trimethylpsoralen induced chromosomal aberrations in Hordeum
vulgare grown under normal daylight and in the presence of ultraviolet
A radiation induced sister chromatid exchanges and chromosomal
aberrations in cultured mammalian cells.
5.3 Human data
One case of melanoma was reported in a patient treated orally with
4,5',8-trimethylpsoralen. In a small series of patients treated
topically with 4,5',8-trimethylpsoralen and ultraviolet radiation, no
skin malignancy was seen after short-term follow-up.
5.4 Evaluation
There is inadequate evidence for the carcinogenicity of
4,5',8-trimethylpsoralen in combination with ultraviolet A radiation
to experimental animals. No data were available to evaluate the
carcinogenicity of 4,5',8-trimethylpsoralen to experimental animals in
the absence of ultraviolet A radiation.
There is inadequate evidence for the carcinogenicity of
4,5',8-trimethylpsoralen to humans.
For definition of the italicized terms, see Preamble Evaluation.
Subsequent evaluation: Suppl. 7 (1987)
Last updated: 22 April 1998