Key Takeaways

Alpha blockers are commonly prescribed to treat high blood pressure, improve urine flow, and lower urinary tract symptoms caused by benign prostatic hyperplasia (BPH or an enlarged prostate gland).
Certain alpha blockers are also used off-label for different conditions. Prazosin can treat nightmares caused by PTSD (post-traumatic stress disorder) or circulation problems. Tamsulosin can help pass kidney stones.
Common side effects of alpha blockers are dizziness, headache, and low blood pressure. Some alpha blockers may cause sexual dysfunction in rare cases.

Alpha blockers are a group of medications commonly used to treat high blood pressure, though they are not the first-choice options. They are also prescribed to improve urine flow and lower urinary tract symptoms caused by benign prostatic hyperplasia (BPH or an enlarged prostate gland). Please continue reading to find out more about alpha blockers.

What is an alpha blocker or α blocker?

Alpha blockers are medications that bind to alpha-adrenergic receptors, which are present in smooth muscles and arteries throughout the body. Alpha blockers block the effects of norepinephrine, which is a part of the sympathetic nervous system which is responsible for the “fight or flight” response.

Other names for alpha blockers are alpha adrenergic blockers, alpha adrenergic antagonists, or α blockers.

As mentioned, alpha blockers work by blocking the effects of a chemical called noradrenaline or norepinephrine, which has a tightening effect on blood vessels. When alpha blockers bind to alpha receptors in the vascular smooth muscle, they block norepinephrine. The pharmacological effects of alpha blockers relax the smooth muscles and the blood vessels.

Vasoconstriction is the tightening of blood vessels. When this happens, it increases peripheral resistance and systemic blood pressure. By relaxing smooth muscles and blood vessels, alpha blockers cause the muscles to relax, such as in the case of enlarged prostates. Additionally, alpha blockers allow better blood flow by relaxing blood vessels, thus, lowering blood pressure.

There are three categories of alpha adrenergic blocking agents:

Nonselective alpha blockers bind to both alpha-1 and alpha-2 receptors.
Selective alpha 1 blockers bind to alpha-1 receptors only.
Selective alpha 2 blockers bind to alpha-2 receptors only.

What are 5 examples of alpha blockers?

Examples of alpha blockers are as follows:

Are alpha blockers used for anxiety?

Alpha blockers are sometimes used off-label to treat nightmares caused by PTSD (post-traumatic stress disorder).

The U.S. Food and Drug Administration (FDA) has approved alpha blockers for the following conditions:

Hypertension (high blood pressure) — Doxazosin, prazosin, terazosin
Benign prostate hyperplasia (BPH or enlarged prostate) — Alfuzosin, doxazosin, silodosin, terazosin, tamsulosin
Certain tumors, such as pheochromocytoma of the adrenal glands and paraganglioma near the carotid arteries in the neck — Phentolamine and phenoxybenzamine

Off-label uses of alpha blockers include:

Phentolamine for skin damage caused by norepinephrine leakage into skin tissues.
Phentolamine for reversal of local anesthesia.
Prazosin for nightmares and sleep disturbances associated with post-traumatic stress disorder (PTSD).
Prazosin for circulation problems associated with Raynaud’s disease.
Tamsulosin for prostatitis (inflammation of the prostate gland) and lower urinary tract symptoms in men (slow urinary stream, hesitancy, urgency, frequency, and nocturia or nighttime urination).
Alfuzosin, doxazosin, silodosin, and terazosin help pass kidney stones that are stuck in the ureters.

What is the main side effect of alpha blockers?

Common side effects of alpha blockers are dizziness, headache, weakness, and fast heart rate.

Alpha blockers can cause orthostatic hypotension or postural hypotension (a sudden drop in blood pressure with a change in posture from lying or sitting to standing), especially after the first dose. When blood pressure drops, it can cause dizziness, lightheadedness, fainting, and falls. The risk is higher in older adults and those with weak bones (risk of fractures). Alpha blockers also should be used with caution in those on blood thinners since they are at higher risk for bleeding caused by falls. Taking alpha blockers before bedtime may reduce the risk of falls since you’re going to sleep after taking the medication.

Other side effects of alpha blockers include retrograde ejaculation (dry orgasm) and priapism (a prolonged and painful erection lasting more than 4 hours). Priapism is an emergency and can lead to permanent impotence if it is not treated in time.

Taking an alpha blocker can also cause reflex tachycardia as a side effect. This is an increase in heart rate when blood pressure drops.

Additionally, taking an alpha blocker such as tamsulosin (Flomax) is associated with an increased risk of intraoperative floppy iris syndrome, a complication during eye surgery.

Who should not take alpha blockers?

Alpha blockers may not be safe for individuals who are pregnant or breastfeeding, undergoing cataract surgery, those with a history of orthostatic hypotension, heart disease, heart failure, kidney disease, circulatory problems, or respiratory infections, or those taking medications to treat erectile dysfunction.

What is the difference between alpha blockers and beta blockers?

Both alpha blockers and beta blockers are antihypertensive drugs that help in lowering blood pressure. However, alpha blockers lower blood pressure by binding to alpha adrenergic receptors, while beta blockers do so by binding to beta-adrenergic receptors.

This means their effects on the body are different. For example, beta blockers have greater effects on the heart and minimal effects on the urinary system. Also, the drug interactions with other drugs and side effects of alpha blockers vs beta blockers are different. For example, beta blockers are less likely to cause adverse effects such as a drop in blood pressure (postural hypotension).

Note: Some beta blockers, such as labetalol, have alpha-1 blocking activity in addition to beta blocking activity. These beta blockers have favorable effects on blood pressure but can cause orthostatic hypotension.

Your healthcare provider will choose the most appropriate antihypertensive therapy for you based on your medical history. Besides alpha blockers and beta blockers, there are other medicines available to improve symptoms of high blood pressure, such as calcium channel blockers, angiotensin II receptor blockers (ARBs), angiotensin converting enzyme (ACE) inhibitors, and diuretics (water pills). These are first-line drugs for high blood pressure.

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References:

https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/alpha-blockers/art-20044214
https://my.clevelandclinic.org/health/treatments/22321-alpha-blockers
https://www.ncbi.nlm.nih.gov/books/NBK556066/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5565133/#
https://pubmed.ncbi.nlm.nih.gov/2571433/#
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2812888/

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