Reference Guide to Alpha Blockers

Highlights 

• Alpha blockers relax the blood vessels and treat high blood pressure and benign prostatic hyperplasia (BPH).

• Nonselective alpha blockers are used before adrenal gland tumor removal to control blood pressure during surgery. 

• Like all medications, alpha blockers have side effects and potential interactions with other drugs. 

Your doctor may prescribe alpha blockers if you have high blood pressure or trouble urinating. These drugs can relax the smooth muscles that line the blood vessels and surround the neck of the bladder. By doing so, they allow blood vessels and the urinary tract to dilate.

What Are Alpha Blockers and What Are They Used For?

Alpha blockers, also called alpha-adrenergic antagonists, are medications that allow doctors to treat certain medical conditions without resorting to surgery. 

Alpha blockers are used for: 

• Hypertension (high blood pressure)
• Benign prostatic hyperplasia (BPH)
• Preparation for surgical removal of cancerous or non-cancerous tumors called pheochromocytomas and paragangliomas 

The off-label (or non-standard) uses of these drugs cover a wider range of conditions: 

• Nightmares and sleep problems resulting from post-traumatic stress disorder (PTSD)
• Circulatory problems resulting from Raynaud’s phenomenon
• Chronic prostatitis and pelvic pain
• Prostate cancer
• Urinary retention
• Heart failure with preserved ejection fraction (HFpEF)

It’s important to note that while alpha blockers are effective for these conditions, they are not the only treatment option and are often used in combination with other medications. The choice of whether to use an alpha blocker and which one to use will depend on your health profile and the specific condition being treated.

How Do Alpha Blockers Work?

Alpha blockers attach to receptors in the blood vessel walls and smooth muscles, causing relaxation. They block the action of norepinephrine, a neurotransmitter that causes muscle contraction and the tightening of blood vessels. By doing so, alpha blockers cause the blood vessels to widen and allow more blood through. With less resistance to the flow of blood, blood pressure drops.

In addition to blood vessels, alpha blockers can also relax the muscles of the bladder neck and prostate to improve the flow of urine, making them useful for the treatment of BPH symptoms. 

Alpha blockers can also improve blood flow to the extremities, making it a useful treatment for Raynaud’s disease.

Alpha Blocker Subtypes

There are two subtypes of alpha blockers: 

• Selective alpha-1 blockers
• Nonselective alpha blockers, which block both type 1 and type 2 alpha receptors

Selective Alpha-1 Blockers

Tamsulosin

Bearing the suffix “-osin,” these drugs are the most frequently used alpha blockers. Doctors may prescribe these medications to treat BPH. They may also use them to control high blood pressure, but for this purpose, these medications aren’t typically first-line options. 

Alpha-1 blockers work by relaxing the smooth muscles around the blood vessels as well as the muscles at the neck of the bladder. As the blood vessels and urine ducts dilate, urine flows through freely, relieving some of the unpleasant symptoms of BPH. 

Here is a list of FDA-approved alpha blockers and their uses based on the most recent data available:

• Tamsulosin (Flomax): Primarily prescribed for the treatment of benign prostatic hyperplasia (BPH). It works by relaxing muscles in the prostate and bladder neck, making it easier to urinate.
• Silodosin (Rapaflo): Also used for the treatment of BPH. Similar to tamsulosin, it eases the flow of urine by relaxing the muscles in the prostate and bladder.
• Alfuzosin (Uroxatral): Indicated for BPH, alfuzosin also relaxes the muscles in the prostate and bladder neck, improving urination flow.
• Doxazosin (Cardura, Carduran, Cascor, Doxadura): This medication is used for both BPH and hypertension. It relaxes the muscles of the blood vessels and the prostate, which helps in lowering blood pressure and improving urine flow.
• Terazosin (Hytrin): Approved for BPH and hypertension, Terazosin can relax the blood vessels and the muscles of the prostate and bladder neck.
• Prazosin (Minipress): While less commonly used for BPH, it is primarily indicated for hypertension. Prazosin relaxes the blood vessels, making it easier for the heart to pump and lowering blood pressure.

Warnings and Contraindications — Selective Alpha-1 Blockers

Never take a selective alpha-1 blocker if you are allergic to the medication or any of its components. If you notice symptoms of an allergic reaction, seek medical help immediately. 

Selective alpha-1 blockers like terazosin may cause light-headedness in patients who start taking the drug or start taking it again after a pause. This light-headedness may escalate to dizziness and fainting. If you notice these side effects, consider taking the drug right before you go to bed. Don’t get up quickly from a lying position, as you may feel dizzy due to the reduced blood pressure. 

Other precautions for those taking this medication include:

• Don’t stop abruptly. If you stop taking a selective alpha-1 blocker and want to restart it, talk to your doctor first. Your dosage may need tweaking. 
• Communication is key. Before an eye surgery, tell your doctor if you’re taking an alpha-1 blocker, as these medications may affect your pupils. Only stop taking the drug if your surgeon tells you to. 
• Special considerations for women. We don’t know whether drugs like terazosin or tamsulosin can harm unborn babies or toddlers by passing into the milk of lactating women. Some alpha blockers are not approved for use by female patients but are used off-label for certain conditions. Get personalized advice from your doctor.
• Keep tabs on your blood pressure. While you’re on this medication, your doctors may want to monitor your blood pressure and/or prostate. Follow their instructions, and don’t stop taking selective alpha-1 blockers on your own, even if you feel well.
• Keep taking your medications. High blood pressure is often symptomless, and you may still have it without realizing it. If you must stop taking selective alpha-1 blockers, let your doctor know.

You may not be able to take an alpha-1 blocker if you suffer from one of these conditions: 

• Sulfa drug allergies
• Kidney disease
• Liver disease
• Prostate cancer
• Low blood pressure 

Always talk to your doctor about all of your medical conditions before beginning a new treatment. Read the medicine label and discuss your concerns with your doctors. 

Side Effects — Selective Alpha-1 Blockers

If you experience the symptoms of an allergic reaction while taking these drugs, seek medical help immediately. Allergy symptoms can include:

• Burning eyes
• Itching
• Swelling of the face, tongue, or mouth
• Urticaria (hives)
• Difficulty breathing 

Less common but more severe side effects of alpha-1 blockers can include: 

• The sensation that you are about to pass out
• Long-lasting, painful erections
• Vomiting
• Constipation 

If you experience any of these symptoms, seek medical help as soon as possible. 

Some of the more frequent but less-severe side effects of alpha blockers are: 

• Dizziness or lightheadedness 
• Loss of libido
• Abnormal ejaculation
• Reduced semen volume
• Cough
• Sore throat
• Diarrhea
• Nausea
• Stuffy nose
• Back pain
• Headaches
• Chest pain
• Insomnia
• Weakness
• Vision problems
• Tooth problems 

While these side effects may not warrant immediate medical attention, don’t hesitate to contact your doctor if you’re worried about them. 

Drug Interactions — Selective Alpha-1 Blockers

• Blood pressure medications: When combined with other antihypertensive agents, such as beta-blockers, diuretics, ACE inhibitors, or calcium channel blockers, alpha-1 blockers can cause an additive hypotensive effect, which might lead to an excessive drop in blood pressure.
• Phosphodiesterase-5 inhibitors: Medications used for erectile dysfunction, like sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra), can also cause a significant drop in blood pressure when taken with alpha-1 blockers.
• Central nervous system (CNS) depressants: Drugs that depress the central nervous system, including opioids, benzodiazepines, and alcohol, may enhance the sedative effects of alpha-1 blockers, leading to increased drowsiness or dizziness.
• Nonsteroidal anti-inflammatory drugs (NSAIDs): NSAIDs may decrease the antihypertensive effects of alpha-1 blockers by inhibiting the production of vasodilating prostaglandins.
• Cimetidine: This medication, used to treat stomach ulcers and gastroesophageal reflux disease (GERD), can increase plasma levels of some alpha-1 blockers, potentially intensifying their effects and side effects.
• Antifungal agents: Certain antifungal drugs, such as ketoconazole, can inhibit the metabolism of alpha-1 blockers, leading to increased blood levels and a higher risk of side effects.
• HIV protease inhibitors: These can also inhibit the metabolism of alpha-1 blockers, increasing their concentration and the risk of adverse effects.
• Other alpha blockers: Using more than one alpha blocker at a time can lead to an increased risk of severe hypotension.
• Warfarin (coumadin): Some alpha-1 blockers may increase the risk of bleeding when taken with warfarin, an anticoagulant.

Note that no drug interaction list is complete. It’s important that you inform your healthcare provider of all medications you’re taking, including over-the-counter drugs and herbal supplements, to avoid potentially harmful interactions with alpha-1 blockers. 

If you notice any new or unusual symptoms after beginning treatment, notify your doctor right away.

Non-Selective Alpha Blockers

Nonselective alpha blockers are primarily used in the management of specific vascular conditions. The three nonselective alpha blockers currently approved by the FDA include: 

• Phenoxybenzamine (Dibenzyline): Approved for the treatment of pheochromocytoma to control episodes of hypertension and sweating.
• Phentolamine (Regitine): Used for the prevention or control of hypertensive episodes that may occur in a patient with pheochromocytoma as a result of stress or manipulation during preoperative preparation and surgical excision.
• Tolazoline: This drug has been used as a vasodilator in the treatment of persistent pulmonary hypertension in newborns.

Nonselective alpha blockers can also be used off-label for other conditions. Phenoxybenzamine, for instance, may be used in certain cases to manage the cardiovascular complications associated with cocaine intoxication, due to its ability to block the effects of catecholamines. 

Warnings and Contraindications — Nonselective Alpha Blockers

Before taking nonselective alpha blockers, talk to your doctor about the medications you take. People who are allergic to these medications should not be exposed to them.

Tell your doctor about any other allergies you may have. 

Your doctor may not give you nonselective alpha blockers if you have ever had one of the following conditions: 

• Hardened coronary arteries
• Other problems with your arteries
• Heart attack
• Chest pain
• Pressure in the chest 

Never stop taking your medication or change your dose without talking to your doctor. 

If you’re already on nonselective alpha blockers, tell your healthcare providers. If you have low blood pressure, nonselective alpha blockers may expose you to additional risks. 

Pregnant and lactating women should talk to their doctors before taking nonselective alpha blockers. 

Side Effects — Nonselective Alpha Blockers

Due to the potential for significant side effects, these medications are typically managed closely by healthcare providers, with careful monitoring of blood pressure and other vital signs to ensure patient safety. 

Seek medical attention immediately if you experience any of the following symptoms:

• Symptoms of an allergic reaction like rash, hives, itching, swollen face, or difficulty swallowing
• Blurred eyesight
• Drooping on one side of the face or weakness in one side of the body
• The feeling of passing out
• Fast heartbeat
• Chest pain
• An abnormally bad headache 

Some of the less-severe possible side effects of nonselective alpha blockers are: 

• Flushing
• Stuffy nose
• Exhaustion
• Vomiting
• Diarrhea
• Pain at the site of the shot
• Dizziness 

Don’t hesitate to call your doctor if any of these side effects persist or get worse. 

Drug Interactions — Nonselective Alpha Blockers

As with all medications, there are potential drug interactions you should be aware of. Be sure that all your providers know if you are taking any of the medications on this list:

• Blood pressure medications: Other drugs that are used to manage high blood pressure may have their effects intensified by nonselective alpha blockers, potentially causing blood pressure to fall to dangerously low levels.
• Epinephrine and norepinephrine: These medications typically increase blood pressure and heart rate, but when taken with nonselective alpha blockers, they can cause a significant drop in blood pressure and a rapid heartbeat because the blockers prevent them from constricting blood vessels as they normally would.
• Reserpine: This drug lowers blood pressure by depleting certain chemicals in the nerves that cause vessels to tighten. When combined with nonselective alpha blockers, the effect on blood pressure can be more pronounced, leading to a greater risk of it becoming too low.
• Tizanidine: This is a muscle relaxer that also lowers blood pressure by reducing nerve signals that tighten blood vessels. When used with nonselective alpha blockers, the combined effect can lead to a substantial decrease in blood pressure.
• Phosphodiesterase-5 inhibitors: These are drugs used to treat erectile dysfunction, such as Viagra, which can also lower blood pressure. When used with nonselective alpha blockers, there’s a risk that blood pressure could become too low, which might lead to lightheadedness or fainting.
• CNS depressants: Medications that have a sedative effect on the central nervous system, like sleeping pills or some painkillers, can have their drowsy effects increased when taken with nonselective alpha blockers, leading to enhanced drowsiness or even deeper sedation. Alcohol is also included in this list.
• Antidepressants: Some antidepressants can affect blood pressure and heart rate. When taken with nonselective alpha blockers, these effects can be unpredictable, sometimes leading to unexpected changes in blood pressure.

No list of drug interactions is ever complete. Nonselective alpha blockers may interact with other medications, vitamins, and herbal supplements. Interactions may vary from one drug to another, so it’s a good idea to check all the medications you’re taking with the Drugs.com Drug Interaction Checker.

A Final Word

Alpha blockers, including both selective and nonselective types, serve as important agents in the management of various medical conditions. While these medications offer significant benefits, it is crucial for patients and healthcare providers to be aware of their potential side effects and drug interactions. 

A thorough understanding of when and how to use alpha blockers will ensure the best outcomes for patients using these treatments.

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