The influence of oral contraceptives on the metabolism of methaqualone in man.

1 Oral contraceptives were shown to suppress the mid-cycle increase in methaqualone metabolism observed in premenopausal women not receiving oral contraceptive therapy. No women were identified in whom this suppression was not observed. 2 Combined oestrogen-progestogen contraceptives produced the effect in all nine women studied. The effect was also observed in one woman who was receiving progestogen-only contraceptives. 3 The effect of the combined contraceptives was observed within one month of the commencement of the contraceptive therapy. 4 The results emphasise the need to monitor the effect of the menstrual cycle in women not receiving oral contraceptive therapy when the effects of such therapy is studied. 5 These effects are more likely to be the consequence of an inhibition of hormonal control of hepatic metabolic activity by the synthetic steroids than they are to simple inhibition of hepatic metabolism.