Interaction with Warfarin

P450 microsomal enzyme inhibitors: (i.e. Drugs that increase the INR and risk of bleed)

Gastrointestinal: Cimetidine, omeprazole and possibly other PPIs
Cardiovascular: Amiodarone(liver enzyme inhibition is low and may persist long after withdrawal)
Anti-fungals(azoles)
Antibiotics: Bactrim(co-trimoxazol), macrolides, metronidazole, quinolones
Anti-depresants: Fluvoxamine, SNRI,SSRI

P450 enzyme inducers: (i.e. that decrease the INR)

Anti-epileptics: carbamazepine, phenobarb, phenytoin
Rifampicin(most potent inducer)
OCP/HRT
Alcohol(Chronic)
Griseofulvin