Fears aroused in patients by migraine.

Griseofulvin modifies hepatic enzyme activity in mice,' so that enzyme induction and a consequent lowering of oestrogen concentra- tions may explain the intermenstrual bleeding on the basis of a withdrawal effect. Amenorrhoea is not so readily explained. Interestingly, however, rifampicin, a potent inducer of hepatic microsomal enzymes, causes the same range of cycle anomalies with intermenstrual bleeding, amenorrhoea, and unintended pregnancies in women using oral contraceptives.2