Class II Antiarrhythmic Drugs
Class II antiarrhythmic drugs are beta adrenergic blockers. They reduce sinus rate, slow atrioventricular nodal conduction and suppress catecholamine-driven automaticity and triggered activity. They are the only antiarrhythmic class that reduces mortality in survivors of myocardial infarction and in heart failure with reduced ejection fraction.
Members used as antiarrhythmics. Esmolol, metoprolol, propranolol, atenolol, bisoprolol, carvedilol, nadolol and landiolol (in some regions). Sotalol combines class II and class III action and is covered with class III drugs.
Mechanism. Blockade of beta-1 receptors reduces cyclic AMP, calcium current and the pacemaker current slope. Sinus rate slows, the atrioventricular nodal refractory period lengthens and the threshold for ventricular fibrillation rises. Reduced sympathetic drive also reduces ischaemia and sudden death after infarction.
Pharmacokinetics. Esmolol is hydrolysed by red cell esterases, with a half-life of about 9 minutes. Propranolol has extensive first pass metabolism and is highly lipophilic. Atenolol, nadolol and sotalol are cleared by the kidney. Bisoprolol has dual clearance.
