What is/are Prazosin?
Prazosin, trade names Minipress, Vasoflex, Pressin and Hypovase, is a sympatholytic drug used to treat high blood pressure and anxiety, PTSD, and panic disorder. It is an alpha-adrenergic blocker that is specific for the alpha-1 receptors. These receptors are found on vascular smooth muscle, where they are responsible for the vasoconstrictive action of norepinephrine. They are also found throughout the central nervous system.
In addition to its alpha-blocking activity, prazosin is an antagonist of the MT3 receptor (which is not present in humans), with selectivity for this receptor over the MT1 and MT2 receptors.
Prazosin is orally active and has a minimal effect on cardiac function due to its alpha-1 receptor selectivity. However, when prazosin is initially started, heart rate and contractility go up in order to maintain the pre-treatment blood pressures because the body has reached homeostasis at its abnormally high blood pressure. The blood pressure lowering effect becomes apparent when prazosin is taken for longer periods of time. The heart rate and contractility go back down over time and blood pressure decreases.
The antihypertensive characteristics of prazosin make it a second-line choice for the treatment of high blood pressure. Prazosin is also useful in treating urinary hesitancy associated with prostatic hyperplasia, blocking alpha-1 receptors, which control constriction of both the prostate and ureters. Although not a first line choice for either hypertension or prostatic hyperplasia, it is a choice for patients who present with both problems concomitantly.
This medication has shown to be effective in treating severe nightmares in children and people with PTSD symptoms. Veterans have also been treated successfully at Seattle's VA Puget Sound Health Care System (VAPSHCS) for sleep disturbance related to PTSD. Doses are lower for this purpose than for control of blood pressure.
Prazosin holds promise as a pharmacologic treatment for alcohol dependence after a 2009 pilot trial l was completed. A larger controlled Phase II trial "Clinical Trial of the Adrenergic Alpha-1 Antagonist Prazosin for Alcohol Dependence" is currently underway, set to be completed November 2013. The drug is usually recommended for severe bitings from Indian Red Scorpion Hottentotta tamulus in Indian Subcontinent.
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 if their blood pressure is not adequately maintained during standing. 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 and fainting, are especially pronounced in the first dose. One very rare side effect of prazosin is priapism. Another possible side effect is dreaming while awake or hallucinations of wakefulness while falling asleep on the medication (see oneirophrenia).
This article uses material from the Wikipedia article Prazosin, which is released under the Creative Commons Attribution-Share-Alike License 3.0.