Enhanced -ve inotropic effect of β-blockers. Fatal ventricular fibrillation w/ verapamil & IV dantrolene. Risk of pulmonary oedema or excessive decreased BP w/ Mg sulphate. Decreased plasma conc by CYP3A4 inducers eg, carbamazepine, phenobarb, phenytoin, fosphenytoin, primidone, rifampicin. Increased plasma conc by CYP3A4 inhibitors eg, cimetidine, itraconazole, grapefruit juice. Increased risk of adverse reactions w/ itraconazole. Elevated plasma cyclosporine, tacrolimus or sirolimus; digoxin levels. Potentiated antihypertensive effect w/ baclofen, α-blockers, TCAs, neuroleptics, opioids, amifostine. Decreased antihypertensive effect w/ IV corticosteroids, tetracosactide. Induced potential additive or synergistic hypotensive effect w/ inhalational anaesth. Enhanced neuromuscular block w/ competitive neuromuscular blockers.