ENZYME INDUCING DRUGS MAY CAUSE FAILURE OF CONTRACEPTIVE BY INCREASING THEIR METABOLISM.FAILURE OF CONTRACEPTION WITH PHENOBARBITONE, PHENYTOIN, PRIMIDONE, CARBAMAZEPINE, DICHLORALPHENAZONE, RIFAMPICIN AND BROAD SPECTRUM ANTIBIOTICS. COMBINATION WITH ETHINYLOESTRADIOL INCREASES INSULIN REQUIREMENT AND REDUCED EFFICACY OF ORAL ANTICOAGULANTS.VIT B6 REDUCES ITS SERUM CONC, SO CHANCES OF CONTRACEPTIVE FAILURE ARE MORE. REDUCES CLEARANCE OF CORTICOSTEROIDS, ALPRAZOLAM SO ENHANCES ITS EFFECT. INCREASES TOXICITY OF CYCLOSPORIN. DECREASED CLEARANCE OF XANTHINES. INCREASED CLEARANCE OF PARACETAMOL, MORPHINE, CLOFIBRATE.