Bretylium (also Bretylium tosylate) blocks the release of noradrenaline from the peripheral sympathetic nervous system, and is used in emergency medicine, cardiology, & other specialties for the acute management of ventricular tachycardia & ventricular fibrilation. It is contraindicated in patients with AV (atrioventricular) heart block or digoxin toxicity. It probably should not be used at other times.