Bretylium

Uses

Anti-adrenergic; cardiac depressant (anti-arrhythmic).

Uses

Bretylium possesses sympatholytic action, which is associated with blockage of norepinephrine (noradrenaline) from presynaptic nerve endings. It also has a direct effect on ischemic myocytes. Bretylium is an urgent treatment that is used in situations of ventricular tachycardia and ventricular fibrillation, primarily in the severe phase of a myocardial infarction, during which use of other medications or procedures have proven unsuccessful. It requires great caution and should be used only in urgent situations.

Definition

ChEBI: A quaternary ammonium cation having 2-bromobenzyl, ethyl and two methyl groups attached to the nitrogen. It blocks noradrenaline release from the peripheral sympathetic nervous system, and is used in emergency medicine, cardiology, and other specialties fo the acute management of ventricular tachycardia and ventricular fibrillation.

brand name

Bretylol (Mayne).

Mechanism of action

Bretylium is poorly absorbed when taken orally, and it is used only in the form of intravenous or intramuscular injections. However, like many other quaternary ammonium salts, it initiates a response of neuronal catechoamines, which can cause tachycardia, elevate blood pressure, and so on.

Clinical Use

Bretylium (Bretylol) was introduced for the treatment of essential hypertension but subsequently was shown to suppress the ventricular fibrillation often associated with acute myocardial infarction.
Bretylium is not to be considered a first-line antiarrhythmic agent. However, because of its ability to prolong the refractory period of Purkinje fibers and to elevate the electrical threshold to ventricular fibrillation, bretylium has been found useful in the treatment of lifethreatening ventricular arrhythmias, especially when conventional therapeutic agents, such as lidocaine or procainamide, prove to be ineffective. In addition, bretylium is known to facilitate the reversal of ventricular fibrillation by precordial electrical shock. Its use should be limited to no longer than 5 days.

Side effects

The most important side effect associated with the use of bretylium is hypotension, a result of peripheral vasodilation caused by adrenergic neuronal blockade (a guanethidinelike action). Nausea, vomiting, and diarrhea have been reported with IV administration and can be minimized by slow infusion. Longer-term problems include swelling and tenderness of the parotid gland, particularly at mealtime.

Synthesis

Bretylium, N-(o-bromobenzyl)-N-ethyl-N,N-dimethylammonium tosylate (18.1.22), is synthesized by reacting o-bromobenzyltosylate with ethyldimethylamine.

Precautions

The associated initial release of catecholamines may result in an excessive pressor response and stimulation of cardiac force and pacemaker activity. The resulting increase in myocardial oxygen consumption in a patient with ischemic heart disease may lead to ischemic pain (angina pectoris). Patients in a state of circulatory shock probably should not be administered bretylium because of its delayed sympatholytic action.

Raw materials

Preparation Products