Cytochrome P450 dependant drugs

Dependant

• Phenytoin
• Theophylline
• Carbamazepine
• Tacrolimus and cyclosporine
• Digoxin
• Flecainide
• Sildenafil
• Simvastatin
• SSRIs SNRIs

Enzyme inducers decrease the amount of active warfarin and decrease its exposure (and INR)

Enzyme inhibitors increase the amount of active warfarin and increase its exposure (and INR)

Drugs that can inhibit P450

• Amiodarone
• Metronidazole
• Ciprofloxacin, levofloxacin
• Erythromycin, clarithromycin
• Grape fruit juice
• SSRIs- sertraline, fluoxetine
• Sodium valproate
• Allopurinol

Drugs that can induce P450 

• Carbamazepine (self inducing)
• Phenytoin (self inducing)
• Rifampin
• St. John's Wort
• Chronic alcohol
• Smoking