Failure of oral contraceptives occur when used with any Of these except.

Tetracycline-Interruption of enterohepatic circulation of the estrogen failure of contraception. Phenytoin induces microsomal enzymes and increases degradation of steroids (failure of oral contraceptives). Rifampin is an microsomal enzyme inducer-increases several CYP450 isoenzymes, including CYP3A4, CYP2D6, CYP1A2, and CYP2C subfamily. It thus enhances its own metabolism as well as that of many drugs including oral contraceptives. (REF. Essentials of Pharmacology TD TRIPATHI 6th EDITION)