(Group 3)

For definition of Groups, see Preamble Evaluation.

VOL.: 66 (1996) (p. 143)

CAS No.: 2955-38-6
Chem. Abstr. Name: 7-Chloro-1-(cyclopropylmethyl)-1,3-dyhydro-5-phenyl-2H-1,4-benzodiazepin-2-one

5. Summary of Data Reported and Evaluation

5.1 Exposure data

Prazepam is a benzodiazepine used since the late 1970s for treatment of anxiety.

5.2 Human carcinogenicity data

No data were available to the Working Group.

5.3 Animal carcinogenicity data

Prazepam was tested for carcinogenicity in one experiment in mice and in one experiment in rats by oral administration in the diet. No significant increase in the incidence of tumours was found.

5.4 Other relevant data

Prazepam is rapidly and extensively absorbed in humans, but its plasma concentrations are low and of short duration as a consequence of its rapid conversion to N-desmethyldiazepam and, to a lesser extent, 3-hydroxyprazepam. The elimination half-life is about 1 h.

Prazepam is extensively metabolized in rats, and the primary metabolite N-desmethyldiazepam is further converted to at least eight derivatives. Oxazepam is the major metabolite in dogs and monkeys. There is no evidence to suggest that prazepam causes any organ toxicity other than effects associated with its pharmacological action on the central nervous system in humans or experimental animals.

There are no data on the teratogenicity of prazepam in humans. In one study, prazepam increased the incidence of short tail and hydrops fetalis (subcutaneous oedema) in rats. In a single study in the rabbit, it was not teratogenic.

The two available studies on genetic effects were negative.

5.5 Evaluation

There is inadequate evidence in humans for the carcinogenicity of prazepam.

There is inadequate evidence in experimental animals for the carcinogenicity of prazepam.

Overall evaluation

Prazepam is not classifiable as to its carcinogenicity to humans (Group 3).

For definition of the italicized terms, see Preamble Evaluation


Last updated 05/22/97

    See Also:
       Toxicological Abbreviations
       Prazepam (PIM 680)