Potentially dangerous to combine w/ dantrolene. Increased adverse effects w/ idelalisib. Elevated plasma levels of cyclosporine, tacrolimus or sirolimus. Decreased plasma conc w/ CYP3A4 inducers (eg, carbamazepine, phenobarb, phenytoin, fosphenytoin, primidone, rifampicin). Increased plasma conc w/ potent CYP3A4 inhibitors (eg, cimetidine, clarithromycin, cobicistat, erythromycin, itraconazole, grapefruit juice, ketoconazole, nelfinavir, posaconazole, ritonavir, telaprevir, telithromycin, voriconazole). Potentiated antihypertensive effect w/ baclofen, urologic α-blockers (alfuzosin, doxazosin, prazosin, silodosin, tamsulosin, terazosin), α-blocking antihypertensive agents (doxazosin, prazosin, urapidil), TCAs (eg, imipramine), neuroleptics, opioids & amifostine. Increased risk of orthostatic hypotension w/ nitrate derivatives or related agents & other orthostatic hypotension-causing medicinal products. Potential additive or synergistic hypotensive effect w/ inhalational anaesthetics. Enhanced negative inotropic effect of β-blockers in cardiac failure (bisoprolol, carvedilol, metoprolol, nebivolol). Possible risk of pulmonary oedema or excessive decrease in BP w/ Mg sulphate. Increased plasma levels of digoxin. Decreased antihypertensive effect w/ IV corticosteroids (glucocorticoids & mineralocorticoids) & tetracosactide (except for hydrocortisone used as replacement therapy in Addison's disease). Reduced dose requirements of vecuronium infusion.