Profound hypotension & AV block w/ verapamil- & diltiazem-type Ca antagonists. Decreased central sympathetic tonus w/ centrally-acting antihypertensive drugs eg, clonidine, methyldopa, moxonodine, rilmenidine. Increased risk of hypotension w/ dihydropyridine-type Ca antagonists eg, nifedipine, antihypertensive agents & other drugs w/ BP-lowering potential eg, TCAs, barbiturates, phenothiazines. Potentiated AV conduction time & increased -ve inotropic effect w/ class I antiarrhythmic drugs eg, disopyramide, quinidine. Potentiated AV conduction time w/ class III antiarrhythmic drugs eg, amiodarone. Additive systemic effects w/ topical β-blockers. Increased AV conduction time & risk of bradycardia w/ parasympathomimetic drugs. Intensified blood sugar-lowering effect w/ insulin & oral antidiabetics. Attenuated reflex tachycardia & increased risk of hypotension w/ anaesth agents. Reduced heart rate & increased AV conduction time w/ digitalis glycosides. Reduced hypotensive effects by NSAIDs. Reduced effects w/ β-sympathomimetic agents eg, isoprenaline, dobutamine. Increased BP & exacerbated intermittent claudication w/ β- & α-adrenoceptors eg, noradrenaline & adrenaline. Severe postural hypotension w/ moxisylyte. Increased risk of bradycardia w/ mefloquine. Enhanced hypotensive effects w/ MAOIs (except MAO-B inhibitors).