Increased plasma conc w/ CYP3A4 inhibitors (eg, ketoconazole, itraconazole, voriconazole, clarithromycin, erythromycin, atazanavir, indinavir, nelfinavir, ritonavir, saquinavir, amiodarone, grapefruit juice). Decreased plasma conc w/ CYP3A4 inducer eg, carbamazepine. Additive effect on QTc w/ other QTc-prolonging drugs or drugs that can disrupt electrolyte levels. Increased serum levels of digoxin or phenytoin. Increased risk of serotonin syndrome w/ MAOIs or other serotonergic drugs eg, tryptophan, triptans, SSRIs, lithium, fentanyl, tramadol, or St. John's Wort. Increased risk of bleeding w/ NSAIDs, aspirin or other drugs that affect coagulation or bleeding. Increased/decreased prothrombin time w/ warfarin. Enhanced response to alcohol, barbiturates & other CNS depressants. General anesth should be discontinued for as long as clinically feasible prior to elective surgery.