May enhance -ve inotropic effect of β-blockers. Fatal ventricular fibrillation w/ dantrolene. Risk of pulmonary edema or excessive decrease in BP w/ Mg sulfate. Decreased plasma conc w/ CYP3A4 inducers (eg, carbamazepine, phenobarb, phenytoin, fosphenytoin, primidone & rifampicin). Increased plasma conc w/ CYP3A4 inhibitors (eg, cimetidine, itraconazole & grapefruit juice). Increased risk of adverse events w/ itraconazole. Elevated plasma levels of cyclosporine, tacrolimus & sirolimus. Increased plasma levels of digoxin. Potentiate antihypertensive effect w/ baclofen, α-blockers, TCAs, neuroleptics, opioids & amifostine. Decreased antihypertensive effect w/ IV corticosteroids & tetracosactide (except for hydrocortisone used as replacement therapy in Addison's disease). Induced potential additive or synergistic hypotensive effect w/ inhalational anesth.