May enhance -ve inotropic effect of β-blockers & may cause heart failure in patient w/ latent or uncontrolled heart failure. Combination w/ dantrolene. Possible risk of pulmonary edema or excessive decrease in BP w/ Mg sulphate. Decreased plasma conc w/ CYP3A4 enzyme inducing agents (eg, carbamazepine, phenobarb, phenytoin, fosphenytoin, primidone & rifampicin). Increased plasma conc w/ CYP3A4 enzyme-inhibiting agents (eg, cimetidine, itraconazole & grapefruit juice). May elevate plasma cyclosporine/tacrolimus levels w/ cyclosporine, tacrolimus or sirolimus. May increase plasma levels of digoxin. Potentiate the antihypertensive effect w/ baclofen, α-blockers, TCAs, neuroleptics, opioids & amifostine. Decreased antihypertensive effect w/ IV corticosteroids & tetracosactide (except for hydrocortisone used as replacement therapy). Potential additive or synergistic hypotensive effect w/ inhalational anesth.