Specific substancesβ-blockers

β-adrenoceptor blocking drugs exert their toxic effects in overdose not only by blocking the β1- and β2-adrenoreceptors, but also by virtue of their blockade of sodium channels. Patients severely poisoned with β-adrenoceptor blocking drugs develop hypotension, marked bradycardia, coma, convulsions and intraventricular conduction defects. Glucagon has been the treatment of choice for severe hypotension, though there is now increasing evidence that insulin-glucose is an effective alternative.