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Alpha-Blockers: Function, Usage, and Side Effects

Alpha-blockers are a class of medications used to treat a variety of medical conditions such as high blood pressure, enlarged prostate, and urinary problems. Read on to learn more about alpha-blockers.

Alpha-blockers, also known as alpha-adrenoreceptor antagonists or alpha-adrenergic blockers, are medications that work by inhibiting a type of receptors inside your body known as alpha-adrenergic receptors or alpha-adrenoceptors.

There are two main types of alpha-adrenergic receptors: alpha-1 receptors and alpha-2 receptors. Alpha-blockers are grouped based on whether they selectively inhibit either alpha-1 or alpha-2 receptors or inhibit both types of receptors. Health care providers use alpha-1 blockers more frequently, and alpha-2 blockers don’t have many uses in human medicine.

Alpha-1 blockers block alpha-1 receptors. There are three types of alpha-1 receptors: alpha-1A, alpha-1B, and alpha-1D adrenergic receptors. These receptors can be found throughout the whole body, and they produce tissue-specific responses when stimulated.

Alpha-1A and 1D receptors are in the bladder, ureters (connecting your kidneys to your bladder), and prostate. When stimulated, they inhibit urine flow. Alpha-1B receptors can be found in blood vessels

Alpha-1 blockers block the alpha-1 receptors from becoming stimulated by norepinephrine. Through this mechanism of action, alpha-blockers can prevent or decrease the negative effects that can result when these receptors are stimulated, such as decreased urine flow and hypertension, also known as high blood pressure.

Alpha-blockers are classified depending on which type of alpha-adrenergic receptor they work on. 

The US Food and Drug Administration (FDA) has approved the following list of alpha-blockers to treat different conditions:

  • Alfuzosin is used to treat benign prostatic hyperplasia (BPH), also called prostate enlargement.
  • Doxazosin is used to treat BPH and hypertension.
  • Prazosin is used to treat hypertension.
  • Silodosin is used to treat BPH.
  • Tamsulosin is used to treat BPH.
  • Terazosin is used to treat BPH and hypertension.

Alpha-2 blockers are mostly used for research purposes and have limited clinical uses, except for mirtazapine, which is used as an antidepressant. Other alpha-2 blockers are used in veterinary medicine, such as atipamezole and yohimbine.

Non-selective alpha-blockers are also sometimes used in human medicine, including:

  • Phenoxybenzamine 
  • Phentolamine 
  • Tolazoline 
  • Trazodone

Most non-selective alpha-blockers are used for medical emergencies such as a hypertensive crisis or overdoses. Other non-selective alpha-blockers, like trazodone, function as antidepressants.

Some people use phytotherapy (using plants to treat diseases) to try to manage conditions that can be treated with alpha-blockers. It’s important to note that scientific evidence doesn’t back many of these treatments.

For example, traditional medicine has used plants such as Prunus africana, Serenoa repens (commonly known as saw palmetto), and Saxifraga stolonifera to treat symptoms of BPH. Although some studies have shown that certain herbal supplements could benefit patients with BPH and other conditions, their effects are still not fully understood, and more research is needed to support their use.

It’s also important to remember that even natural supplements and herbal substances can produce side effects. These compounds can also interfere with other medications you’re currently taking.

If you’re interested in trying natural alternatives to alpha-blockers, you should always discuss it with your health care provider first. Don’t stop or change your treatment without asking your health care provider, since this could lead to complications.

Unlike beta blockers, alpha-blocker drugs aren’t typically used as the first treatment for hypertension. Instead, they’re often combined with other drugs, such as diuretics, to manage high blood pressure. 

Alpha-blockers work by preventing a hormone called norepinephrine from binding to your alpha-adrenergic receptors. When norepinephrine stimulates these receptors, your arteries and veins tighten and constrict. As a result, your blood flows through a narrower space, which elevates your blood pressure. 

When you take alpha-blockers, your veins and arteries are able to dilate, putting less pressure on your blood vessels, improving circulation, and lowering blood pressure.

Alpha-blockers can also be used to relax other muscles in your body, particularly in the lower urinary tract. Because of this, they can be used to improve urinary flow in patients with conditions such as BPH and urinary tract dysfunction.

If you have high blood pressure or hypertension, your health care provider might prescribe an alpha-1 blocker as part of your treatment. Alpha 1 blockers for hypertension include doxazosin, prazosin, and terazosin.

Alpha-blockers for hypertension are usually used along with other medications. Alpha-blockers can cause more incidences of low blood pressure and related events than other hypertension drugs, so they aren’t prescribed as often as other types of medications.

BPH can lead to lower urinary tract symptoms, such as incomplete bladder emptying, urine retention, an increased risk of urinary infections, sepsis, and chronic kidney disease. 

Several alpha-1 blockers (alfuzosin, doxazosin, tamsulosin, and terazosin) have been approved to help manage symptomatic BPH. Some of these medications could cause side effects such as low blood pressure and ejaculatory dysfunction. These adverse effects are usually dose-dependent. A certified health care provider should always be in charge of prescribing these medications at the correct dose.

Alpha-1 blockers can be useful for patients with both BPH and hypertension. In these patients, alpha-1 blockers may be used to manage both conditions at once.

Lower urinary tract dysfunction can cause symptoms such as increased urinary frequency and urgency, incontinence, and incomplete bladder voiding. Traditional management strategies for this condition include pelvic floor muscle training, lifestyle changes, and behavioral therapy. 

Recently, research has shown that alpha-1 blockers such as terazosin could be helpful in the management of lower urinary tract dysfunction in women. Some research has found that this medication could be particularly helpful for symptoms such as urgency and straining, but more research is needed.

Just like any other medication, alpha-blockers can cause side effects in some people. Alpha-blockers can also have a “first-dose effect,” meaning that they may cause symptoms the first time you take them. These symptoms include low blood pressure and dizziness, which is why health care providers recommend taking the first dose at bedtime and never before donating blood.

Other potential side effects of alpha-blockers include:

  • Headaches
  • Nausea
  • Pounding heartbeat or palpitations
  • Weakness or fatigue
  • Dizziness
  • Orthostatic hypotension (sudden drop in your blood pressure when you sit or stand up)
  • Sleep disturbances

Alpha-blockers can also interact with other medications. Before taking alpha-blockers, it’s important to discuss your medical history and other medications you take with your health care provider.

Alpha-blockers are used to lower blood pressure, improve urine flow, and treat prostate problems and lower urinary tract dysfunction.

When used correctly, alpha-blockers can be beneficial for patients with conditions such as hypertension and benign prostatic hyperplasia.

Although any medication can cause adverse reactions, alpha-blockers are generally considered to be safe, as long as you take them according to your health care provider’s orders. It’s always important to take your medications exactly as they were prescribed and avoid skipping your medications or changing your treatment without first consulting your health care provider.