Increased depressant effect w/ class I antiarrhythmics eg, quinidine, disopyramide, lidocaine, phenytoin; flecainide, propafenone. Reduced heart muscle contractility & delayed AV impulse conduction w/ verapamil- & diltiazem-type Ca antagonists. Reduced heart rate & cardiac output w/ centrally-acting BP-lowering medicines eg, clonidine, methyldopa, moxonodine, rilmenidine. Increased hypotension w/ dihydropyridine-type Ca antagonists eg, nifedipine, felodipine, amlodipine. Increased inhibitory effect on AV impulse conduction w/ class III antiarrhythmics eg, amiodarone, parasympathomimetics. Additive systemic effects w/ topical β-blockers. Increased blood sugar-lowering effect of insulin or oral antidiabetics. Increased risk of cardiodepressive action w/ anaesth agents. Increased impulse conduction time & reduced heart rate w/ digitalis glycosides. Reduced BP-lowering effect w/ NSAIDs. Reduced effect w/ β-sympathomimetics eg, isoprenaline, dobutamine. Increased BP w/ sympathomimetics that activate both β- & α-adrenoceptors eg, noradrenaline, adrenaline. Increased BP-lowering effect w/ TCAs, barbiturates, phenothiazines. Increased bradycardia w/ mefloquine. Enhanced hypotensive effect w/ MAOIs.