Animal tests suggest no cancer risk for the pill

Tests carried out over several years on rats and mice for the possible carcinogenicity of the constituents of oral contraceptives have satisfied the British Committee on Safety of Medicines that there is no carcinogenic hazard to women. The experiments are discussed in a recent publication of the Committee and were continued at varying dosages for most of the lives of the animals involved (both male and female). Progestagens and estrogens were tested both separately and together at a low dose (2-5 times the human dose), a medium dose (50-150 times the human dose), and a high dose (200-400 times the human dose). Only at the medium and high doses were any benign or malignant tumors found in any organs, and these were not always seen in both species of animal tested. While the results are complex, and it is difficult to transfer the experience gained with 1 species to another, the Committee concluded: "Although a carcinogenic effect can be produced when some of the preparations are used in high doses throughout the life-span in certain strains of rat and mouse, this evidence cannot be interpreted as constituting a carcinogenic hazard to women when these preparations are used as oral contraceptives." Long-term experiments on dogs and primates are continuing in the US, and their results will be carefully s crutinized by the Committee when they become available. On present evid ence, however, based on the results of the rat and mice experiments and the added clinical experience and physiological knowledge of the last few years, the Committee has opened the way for a number of new Pills to be licensed for the British market. 10 new preparations are expected to appear - 5 "minipills" or progestagen-only preparations, of which 3 have already been registered, 4 combined oral contraceptives, and 1 sequential preparation.