Other Drugs That Inhibit Adrenergic Neurons

Other Drugs That Inhibit Adrenergic Neurons 

Several agents are available that inhibit activity at adrenergic synapses by interfering with the release of norepinephrine. Rather than directly blocking the postsynaptic receptor, these drugs typically inhibit or deplete the presynaptic terminal of stored norepinephrine. These drugs are used primarily to decrease peripheral adrenergic influence and to treat problems such as hypertension and cardiac arrhythmias. 

Metyrosine (Demser). Metyrosine inhibits the enzyme initiating catecholamine synthesis (epinephrine, norepinephrine) this drug is used to diminish catecholamine stores prior to removal of a catecholamine-producing tumor (pheochromocytoma). 

Orthostatic hypotension is occasionally a problem with the aforementioned drugs, and dizziness and syncope sometimes occur after a sudden change in posture. Some patients also experience gasnointestinal disturbances including nausea, vomiting, and diarrhea. Peripheral edema as evidenced by swelling in the feet and legs has also been reported. 

This chapter classifies and describes a variety of drugs according to their stimulatory (agonistic) or inhibitory 

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Other Drugs That Inhibit Adrenergic Neurons... 

The antihypertensive mechanism of the rauwiloid alkaloids primarily involves depletion of catecholamines from stores by blocking their reuptake mechanism and thereby storage in neuronal vesicles. The effect is widespread both peripherally and centrally, and includes NE, DA, and 5-HT (serotonin). Depletion of the amines affects blood vessels, the heart, adrenal medulla, and possibly other tissues as well. Since it is the reuptake and not the release of NE that is inhibited in the postganglionic adrenergic neuron, the existing pool must be fully depleted before antihypertensive effects become apparent. The drug also binds to vesicular membranes for days, accounting for the irreversibility of the process. 

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