May increase level/effect of amifostine, antihypertensive, CYP1A2 substrate, hypotensive agent, Mg salt, neuromuscular blocker (nondepolarizing), nitroprusside, phenytoin, rituximab, tacrolimus. Level/effect may be increased by α1
-blocker, antifungals (azole derivative, systemic), Ca channel blocker (nondihydropyridine), cyclosporin (systemic), CYP3A4 inhibitor (moderate/strong), dasatinib, diazoxide, fluconazole, macrolides, Mg salt, MAOI, pentoxifylline, phosphodiesterase-5 inhibitor, prostacyclin analogue, PI, quinupristin. May decrease level/effect of clopidogrel, quinidine. Level/effect may be decreased by barbiturate, Ca salt, carbamazepine, CYP3A4 inducer (strong), deferasirox, methylphenidate, nafcillin, rifamycin derivative. Increased level w/ grapefruit juice. Decreased level w/ St. John's wort. Avoid dong quai (has estrogenic activity); ephedra, yohimbine, ginseng may worsen HTN. Increased antihypertensive effect w/ garlic.