Prazosin, brand name Minipress®, is a medication used to treat high blood pressure (hypertension). It belongs to the class of alpha-adrenergic blockers, which lower blood pressure by relaxing blood vessels. Specifically, prazosin is selective for the alpha-1 receptors on vascular smooth muscle. These receptors are responsible for the vasoconstrictive action of norepinephrine, which in turn raises blood pressure. By blocking these receptors, prazosin reduces blood pressure.

Other features which add to the therapeutic value of Prazosin

1) The drug is orally active.

2) Unlike other less selective alpha blockers, which often cause reflex tachycardia through the sympathetic baroreflex response that increases cardiac output, prazosin has a minimal effect on cardiac function due to its alpha-1 receptor selectivity.

3) Prazosin is also useful in treating urinary hesitancy associated with prostatic hyperplasia by blocking alpha-1 receptors, which control constriction of both the prostate and ureters.

Side effects of prazosin include orthostatic hypotension, syncope, and nasal congestion. The orthostatic hypotension and syncope are associated with the body's poor ability to control blood pressure without active alpha-adrenergic receptors. Patients on prazosin should be told not to stand up too quickly, since their poor baroreflex may cause them to faint as all their blood rushes to their feet. The nasal congestion is due to dilation of vessels in the nasal mucosa. One phenomenon associated with prazosin is known as the "first dose response", in which the side effects of the drug, especially orthostatic hypotension, are especially pronounced after the first dose.

Alpha blockers

Prazosin | Prazosine