Adrenergic release inhibitor

Chemical structure of Guanethidine

An adrenergic release inhibitor is a type of medication that inhibits the release of norepinephrine and other catecholamines from the sympathetic nervous system. These inhibitors are primarily used in the treatment of hypertension and certain types of heart failure.

Mechanism of Action

Adrenergic release inhibitors work by interfering with the normal process of neurotransmitter release from sympathetic nerve endings. This is typically achieved by blocking the vesicular monoamine transporter (VMAT), which is responsible for the uptake of norepinephrine into synaptic vesicles. By preventing the storage of norepinephrine, these drugs reduce the amount of neurotransmitter available for release into the synaptic cleft.

Guanethidine

Guanethidine is a well-known adrenergic release inhibitor. It is a peripheral sympatholytic agent that was once widely used to manage hypertension. Guanethidine works by displacing norepinephrine from its storage vesicles in the nerve endings, leading to a gradual depletion of norepinephrine stores. This results in a reduction of sympathetic tone and a decrease in blood pressure.

Pharmacokinetics

Guanethidine is absorbed from the gastrointestinal tract and is distributed throughout the body. It is not metabolized by the liver and is excreted unchanged in the urine. The onset of action is slow, and the effects can last for several days after discontinuation of the drug.

Side Effects

Common side effects of guanethidine include orthostatic hypotension, bradycardia, and gastrointestinal disturbances. Due to its mechanism of action, it can also cause nasal congestion and sexual dysfunction.

Clinical Uses

Adrenergic release inhibitors like guanethidine are primarily used in the management of hypertension. They are particularly useful in cases where other antihypertensive agents are ineffective or contraindicated. However, due to the availability of newer drugs with fewer side effects, the use of guanethidine has declined.

Related Pages

• Sympathetic nervous system
• Hypertension
• Norepinephrine
• Peripheral sympatholytic