Interaction between certain psychopharmaca and low-dose oral contraceptives.

Whether commonly prescribed benzodiazepine sedatives or hypnotics interact with low-dose oral contraceptive formulations used in Hungary was explored by recording incidence of breakthrough bleeding in women taking both of these types of drugs. 72 women taking Rigevidon or Anteovin (Chemical Works of Gedeon Richter, Ltd, Budapest) during 1989- 1988, and 1 of 4 benzodiazepines, were followed for 1/2 to 2 cycles. The drugs included: diazepam (Seduxen) 1 to 3 x 5 mg, nitrazepam (Eunoctin) 5-10 mg, chlordiazepoxide (Elenium) 2 to 4 x 5 mg, or meprobamate (Andaxin) 1 - 3 x 200 mg. No pregnancies occurred in 25 (36.1%), usually limited to spotting (30.6%). Most of the bleeding was reported during intake of chlordiazepoxide or meprobamate (23 cases). In 19 of these women, bleeding did not occur in the subsequent cycle when the sedative trioxazin (Ruditel) was substituted, corroborating the interpretation that a drug interaction had occurred with the original agents.