Drug which interferes effectiveness of OCP are all, EXCEPT:
Contraceptive failure may occur if the following drugs are used concurrently: Enzyme inducers like Phenytoin, Phenobarbital, primidone, carbamazepine, rifampin. It will increase the metabolism of estrogenic as well as progestational component. Suppression of intestinal microflora: Tetracyclines and ampicillin etc. No deconjugation of estrogens excreted in bile-their enterohepatic circulation is interrupted-blood levels fall. Also Know: Absolute Contraindication of OCP: Thromboembolic, coronary and cerebrovascular disease or history of it Moderate to severe hypeension Hyperlipidemia Active liver disease Hepatoma H/o of jaundice during past pregnancy Malignancy of Breast/genitalis Porphyria Impending major surgery- to avoid postoperative thromboembolism. Ref: K.D.T. 6th Ed Page 317
Aspirin
Phenobarbital
Rifampicin
Primidone