| Acetaminophen/APAP |
↑ with higher doses |
Limit APAP to 2000mg/day |
| Alcohol |
↑ with binging
↓ with cronic use |
Limit to 1-2 EtOH drinks/day |
| Amiodarone |
slow ↑ over time |
Complex interaction that takes place over 6-8 weeks. Ultimately expect 25-50% warfarin dose reduction. Check INR q1-2 weeks and make serial adjustments per INR. |
| Bosentan (Tracleer) |
↓ |
|
| Capecitabine (Xeloda) |
↑ |
|
| Carbamazepine |
↓ |
|
| Dicloxacillin |
↓ |
More significant if course >14 days. |
| Doxycycline |
↑ |
Not always clinically significant if pt not systemically ill. |
| Fibrates |
↑ |
|
| Flu Vaccine |
↑ |
Varies from year to year, but may cause transient rise in INR. |
| Fluconazole |
↑ |
Hold warfarin x1 for single dose. Expect 25-50% warfarin dose reduction for extended course. |
| Fluoroquinolones |
↑ |
Not always clinically significant if pt not systemically ill. |
| Mercaptopurine |
↓ |
|
| Metronidazole (Flagyl) |
↑ |
Expect 25-50% warfarin dose reduction. |
| Phenytoin |
↓ or ↑ |
Complex interaction: initially ↑ INR, but then ↓ after prolonged administration. Additionally, warfarin may alter serum phenytoin concentrations. |
| Rifampin |
↓ |
Expect 2- to 5-fold increase in warfarin dose requirements. |
| Sulfamethoxazole (Septra/Bactrim) |
↑ |
Expect 25-50% warfarin dose reduction |
| Testosterone |
↑ |
|