Increased plasma level w/ CYP450 inhibitors eg, macrolide antibiotics (erythromycin, clarithromycin, troleandomycin, spiramycin, josamycin), azole antimycotics (ketoconazole, itraconazole), PIs (ritonavir, indinavir) or cimetidine. Increased risk of vasoconstriction w/ ergotamine, selective vascular 5HT
1 receptor agonists or nicotine (eg, smoking). Combination w/ β-blockers.