Prazosin: characteristics and side effects of this drug.

A summary of the characteristics of this drug of the quinazoline group.

Arterial hypertension is a disease with a high incidence in the population. Both prevention and treatment are essential, since it is one of the most important risk factors for the development of cardiovascular diseases. In order to alleviate its symptoms, drugs such as prazosin, a medication that acts by relaxing the blood vessels so that blood flows better, can be used.

In this article we explain what is prazosin and what it is used for, what is its mechanism of action, for what other type of disorders it is usually used, and what are its main side effects.

Prazosin: what is it and what is it used for?

Prazosin is a medication used primarily to treat high Blood Pressure or arterial hypertension. It belongs to the group of antiadrenergic drugs, also called alpha blockers or sympatholytics, which are characterized by blocking the body's sympathetic activity and facilitating the circulation of oxygen and blood in the body, thereby reducing the risk of serious health problems, such as heart attack or stroke.

This drug, marketed for clinical purposes in the U.S. in 1976, is classified within the group of quinazolinesIts chemical profile is very similar to that of other compounds such as doxazosin or terazosin, both alpha-blocker drugs used in arterial hypertension and in the improvement of various urinary symptoms.

In addition to dealing with hypertension, prazosin is also used in the treatment of benign prostatic hyperplasia (non-cancerous enlargement of the prostate), in congestive heart failure, for pheochromocytoma (a tumor of the adrenal glands), to alleviate sleep difficulties associated with post-traumatic stress disorder, or in the treatment of Raynaud's disease (a rare disorder that causes narrowing of the blood vessels and affects the feet and hands).

Clinical studies with prazosin conclude that prazosin, while not a first-line option for hypertension or prostatic hyperplasia, is an option in patients who present with both disorders concomitantly. In addition, there is evidence that this drug there is evidence that this drug is effective in the treatment of nightmares, especially those related to prostatic hyperplasia, but it is an option in patients with both disorders concomitantly.especially those related to post-traumatic stress disorder.

Mechanism of action

As mentioned above, prazosin belongs to the group of antiadrenergic drugs or alpha-blockers. This means that it acts as an antagonist of the alpha-adrenergic receptors, which are activated by two main catecholamineswhich are activated by two main catecholamines: adrenaline and noradrenaline.

These receptors are essential for blood pressure regulation and are divided into two classes: α1 and β1 adrenoreceptors, which are located on the postsynaptic membrane and receive the signal from noradrenaline; and α2 and β2 adrenoreceptors, which are in contact with catecholamines and facilitate (β2) or inhibit (α2) the release of noradrenaline.

Prazosin inhibits postsynaptic α1-adrenoceptors. This inhibition blocks the vasoconstrictor (constricting) effect of catecholamines (adrenaline and noradrenaline) on vessels, leading to dilation of peripheral blood vessels. Through constriction of blood vessels by activation of the adrenergic receptor, the two catecholamines act to increase blood pressure.

Likewise, prazosin exerts an antagonistic effect on the α1b adrenoreceptor, resulting in dilation of the veins and arteriesThis leads to dilation of veins and arteries, together with a decrease in peripheral vascular resistance, as well as venous return and cardiac filling.

On the other hand, prazosin does not alter the heart rate in people with hypertension. In addition, this drug significantly decreases systemic and pulmonary venous pressure, as well as right atrial pressure in patients with congestive heart failure, although it has been observed that cardiac output is usually increased.

Effects on blood pressure

The pharmacodynamic and therapeutic effect of prazosin includes a decrease in blood pressure, as well as clinically significant decreases in cardiac output, heart rate, blood flow to the kidney, and glomerular filtration rate. The decrease in blood pressure can occur in both the standing and supine positions.

Many of the above effects are due to the vasodilation of blood vessels produced by prazosin, which results in a decrease in peripheral resistance. This refers to the level of resistance of the blood vessels to blood flowing through them. As the blood vessels constrict (narrow), the resistance increases and they dilate (widen), and the peripheral resistance decreases, lowering blood pressure.

Prazosin and Post-Traumatic Stress Disorder

Currently, the pharmacological treatment indicated for the treatment of post-traumatic stress disorder (PTSD) is based on the administration of the antidepressants sertraline and paroxetine. These are effective in controlling symptoms, but generally do not improve the sleep problems that can accompany PTSD.

Research suggests that prazosin may improve sleep in patients suffering from insomnia related to nightmares and PTSD caused by hyperarousal. caused by hyperarousal. As this effect likely occurs through inhibition of the adrenergic stimulation found in hyperarousal states, prazosin may be useful in this regard, helping to improve general symptoms such as flashbacks, startle response, and irritability or anger.

Most of the clinical studies conducted with prazosin have focused on male combat veterans and the results conclude that this drug helps patients sleep more and have fewer nightmares and awakenings. It would also help decrease the severity of other PTSD symptoms, such as re-experiencing a traumatic event.such as re-experiencing a traumatic event, avoiding certain experiences, or feeling overexcited by such symptoms....

Although there have been several studies corroborating the efficacy of prazosin in the treatment of sleep difficulties in PTSD, this should not preclude further extensive research on this drug, especially to determine its clinical usefulness in other populations (especially women and people with PTSD who are not combat veterans) and the optimal doses or frequency with which prazosin should be administered.

Side effects

The consumption of prazosin can cause a series of side effects that, in general, are usually alleviated by decreasing the dose or spontaneously by themselves. The most common include somatic symptoms, gastrointestinal disturbances, fatigue...

Drug-induced syncope may also occur, which may be preceded by tachycardia and is usually unpredictable. This type of syncope can be alleviated by reducing the dose or by administering the drug with food.

However, it should be noted that the most common adverse reactions are usually the following:

• Headache
• Dizziness
• Tiredness
• Blurred vision
• Nausea
• Vomiting
• Diarrhea or constipation
• Abdominal and joint pain
• Urinary incontinence
• Nasal congestion
• Impotence or priapism
• Fever and excessive sweating (diaphoresis)
• Aturdimiento o sensación de mareo al ponerse de pie, especialmente tras la ingesta de la primera dosis o poco después de tomar una dosis durante la primera semana del tratamiento.
• Hipotensión ortostática

Referencias bibliográficas:

• Bendall, M. J., Baloch, K. H., & Wilson, P. R. (1975). Side effects due to treatment of hypertension with prazosin. British medical journal, 2(5973), 727.
• Hudson, S. M., Whiteside, T. E., Lorenz, R. A., & Wargo, K. A. (2012). Prazosin for the treatment of nightmares related to posttraumatic stress disorder: a review of the literature. The primary Care Companion to CNS disorders, 14(2).
• Kung, S., Espinel, Z., & Lapid, M. I. (2012, September). Treatment of nightmares with prazosin: a systematic review. In Mayo Clinic Proceedings (Vol. 87, No. 9, pp. 890-900). Elsevier.