Cytochrome P450 (CYP450) enzymes are a family of enzymes involved in the metabolism of many drugs. Warfarin, an oral anticoagulant, is metabolized mainly by CYP2C9, CYP1A2, and CYP3A4 isoenzymes in the liver.
Some drugs can either inhibit or induce CYP450 enzymes, thereby altering the metabolism of co-administered drugs like warfarin:
- Ciprofloxacin and Metronidazole are CYP450 inhibitors. They reduce the metabolism of warfarin, increasing its plasma concentration and thus enhancing its anticoagulant effect, which can lead to bleeding.
- Diltiazem is a calcium channel blocker that also acts as a CYP3A4 inhibitor. It similarly raises warfarin levels by decreasing its metabolism.
- Carbamazepine, an anticonvulsant, is a CYP450 enzyme inducer, especially of CYP3A4. It increases the metabolic rate of warfarin, leading to reduced plasma levels and a decreased anticoagulant effect, which may cause therapeutic failure.
Thus, among the given options, carbamazepine is the correct choice as it induces hepatic CYP450 enzymes, lowering the effectiveness of warfarin.