Concomitant use w/ drugs that may affect serotonergic neurotransmitter systems eg, SSRIs, MAOIs, triptans, linezolid, lithium or St. John's Wort. Potential serotonin syndrome w/ triptans. Alters effect (including elevation of prothrombin times) of warfarin. Tramadol: Metabolic clearance may be reduced w/ inhibitors of CYP2D6 (eg, quinidine, fluoxetine, paroxetine & amitriptyline) & CYP3A4 (eg, ketoconazole & erythromycin). Reduced analgesic effect w/ carbamazepine. Increased conc w/ quinidine. Digoxin toxicity.