What Are The Side Effects Of Doxazosin?

Doxazosin is a prescription medication commonly used to treat enlarged prostate (benign prostatic hyperplasia) in men. 

It is also an anti-hypertensive medication, albeit not used as the first-line treatment. 

Doxazosin was approved by the U.S. Food and Drug Administration in 1990. 

Since then, doxazosin has been sold by pharmaceutical companies under several brand names, including Cardura, Cardura xl, and doxazosin mesylate. 

Like all medications, doxazosin can come with side effects.

Keep reading to learn the side effects of doxazosin, how long they last, and how to reduce them.

What is doxazosin?

Doxazosin falls under a class of drugs known as alpha-blockers. The medication works by blocking the effect of the flight or fight hormones (adrenaline and norepinephrine). 

These hormones relax the muscles in your prostate gland and bladder neck, allowing urine to pass through more easily. 

Therefore, doxazosin does not actually shrink the prostate gland; it only helps relieve BPH symptoms

Examples are difficulties initiating urination, weak urine stream, incomplete bladder emptying, and a frequent insuppressible urge to urinate, especially during the middle of the night. 

For people with hypertension, doxazosin exerts the same muscle-relaxing effect on blood vessel walls. 

As a result, blood vessels dilate, reducing the resistance for the bloodstream to flow through, thus lowering blood pressure. 

Other off-label uses of doxazosin include facilitating ureteric stones expulsion and treating nightmares associated with post-traumatic stress disorder (PTSD).

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What are the side effects of doxazosin?

Like any other medication, doxazosin has its side effects. However, the most common side effects are mild, and severe side effects are rare.

Common side effects

The below common side effects occur in more than 1 in 10 people:

  • Dizziness or vertigo (feeling of spinning)
  • Fatigue
  • Headache
  • Edema (limbs swelling, puffy eyes and face after waking up from sleep)
  • Rhinitis (runny and stuffy nose)
  • Urinary tract infection symptoms, including an increased need and irresistible urge to pee, pain or a burning sensation when peeing, and smelly or cloudy urine.
  • Abdominal pain
  • Nausea, indigestion, or heartburn
  • Mild hypotension, usually induced by inappropriate dosing of doxazosin
  • Asymptomatic leukopenia (low white cell count) 

Rare and severe side effects

Severe hypotension

A sharp reduction in blood pressure usually happens in people taking doxazosin for the first time or when the medication dosage is adjusted. 

As mentioned before, it is not uncommon for people to develop dizziness or lightheadedness due to mild hypotension after taking doxazosin. 

However, when the blood pressure goes too low, it can be dangerous. Therefore, it is best for you to monitor your blood pressure daily, especially if you are taking other medications that lower your blood pressure.

Intraoperative Floppy iris syndrome (IFIS)

IFIS can happen during cataract surgery in someone taking alpha-blocker medications (including doxazosin). 

Inform your healthcare providers if you are taking or have taken doxazosin before undergoing your cataract surgery.


Priapism is a condition characterized by a painful erection that cannot be relieved by having sex or lasts more than 2 hours. 

It is a medical emergency. If left unattended, you may not be able to have an erection in the future. 


Anaphylaxis is the most severe form of allergy. Symptoms include skin reactions (itchy, swollen, peeling skin with rash and blisters), swollen mouth, face, lips, tongue or throat, tight chest or throat, difficulty breathing or talking, and noisy breathing (wheezing). 

Anaphylaxis may cause death in minutes, so call an ambulance or go to the emergency department immediately.

Cardiovascular problems

This includes heart failure and stroke. Take note if you get chest pain, irregular heartbeats, or you can feel your heart pounding (palpitations). These symptoms may indicate problems in your heart. 

If you are the caregiver of someone taking doxazosin, offer immediate help if you notice they are having signs of stroke, including a sudden drop of arms and legs, face drooping on one side of the face, slurred speech, and confusion or difficulty understanding speech.

Are there any long-term side effects of taking doxazosin?

Despite being an efficient FDA-approved anti-hypertensive drug, some guidelines did not recommend doxazosin in treating hypertension. 

It is now mainly used as a second-line or an add-on drug for hypertension therapy. Why is that so?

In 2000, the ALLHAT trial conducted by researchers from the U.S. National Heart, Lung, and Blood Institute (NHLBI)revealed ground-breaking findings. 

After taking medications for 4 to 8 years, patients assigned with doxazosin have a higher rate (4% on average) of developing several types of cardiovascular diseases, especially stroke (19% higher) and heart failure (100% higher, a doubled risk). 

Therefore, if you have or had cardiovascular diseases, inform your doctor when discussing your treatment for benign prostate hyperplasia (BPH). 

Your doctor might conduct further detailed evaluations and recommend the best treatment plan for you. 

How long do the side effects last? 

Most side effects of doxazosin are mild and will go away after a short while. However, if you experience side effects that last for days or if they are giving you stress, let your doctor knows. 

Your doctor may need to adjust your medication dosage and provide further guidance, such as when and how to take the medication.

Are there any side effects of stopping doxazosin?

A recent review found that when people stop taking alpha-blockers (including doxazosin) for 3 months, their LUTS symptoms significantly worsen, and urine flow is slower too.

Stopping doxazosin without proper planning does more harm than good. Talk to your healthcare providers if the side effects related to doxazosin bother you. They can discuss alternatives with you if needed.

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How to reduce the side effects of doxazosin?

Although side effects of doxazosin are generally unavoidable, there are things you can do to minimize the impact of these unfavorable effects. 

The rule of thumb is you should know how to take the medication. 

  • If you were prescribed an extended-release doxazosin tablet (Cardura XL), you should swallow the tablet as a whole. Do not split, chew or crush it. 
  • Take the medication at a fixed time daily. If you missed a dose, take it as soon as you remember. 
  • However, you may skip the missed dose if it is almost time for the next dose. Do not take a double dose at once.
  • If you missed two or more doses, tell your doctor, as you may need to readjust the dosage of your medication.

Unfortunately, if you still experience side effects after taking the medication correctly, the below tips may help you cope with your symptoms.

Dizziness, vertigo, and fatigue

  • Stop doing things on hand. Instead, sit or lie down and rest until you feel better. Do not drive, use tools or machinery, or do dangerous chores.
  • Sit up from a lying position slowly, especially when getting out of bed in the morning.
  • Rest your feet on the floor for a few minutes before standing up.
  • Avoid drinking alcohol. It will make you feel worse. 
  • If you feel sleepy after taking the medication, tell your doctor, as you may be allowed to switch your medication dosing to nighttime.


  • Have enough sleep and rest.
  • Drink plenty of fluids. 
  • Avoid bingeing on alcohol. 
  • Ask your pharmacist or healthcare provider if you can take an over-the-counter painkiller.

Edema (swollen limbs, puffy eyes, and face)

  • Put your limbs, or the swollen parts, in a higher position.
  • Massage the swollen body parts. 

Urinary tract infection symptoms

  • Seek medical attention, as you need careful evaluation and treatment. 
  • Take enough rest.
  • Drink plenty of fluids, which helps flush out bacteria.

Abdominal pain

  • Reduce your speed when eating and drinking.
  • Have frequent meals in smaller portions. 
  • Ask your pharmacist or healthcare provider if you can take an over-the-counter painkiller.
  • Place a warm water bottle or bag on your stomach.

Nausea, indigestion, or heartburn

  • Take doxazosin after meals unless otherwise specified by your healthcare providers.
  • Avoid oily or spicy food. 
  • Drink plenty of fluids if you vomit to avoid dehydration.
  • Eat or drink slowly in smaller portions.

Who should not take doxazosin?

Before taking doxazosin, tell your healthcare provider about all of your medical conditions and the drugs or supplements you are taking. This is particularly important if you:

  • Have a history of low blood pressure, especially after taking other medications. Signs of low blood pressure include fainting, dizziness, and lightheadedness
  • Have any planned eye surgery
  • Are pregnant or plan to become pregnant
  • Have prostate cancer or a history of prostate cancer
  • Have liver problems
  • Are breastfeeding or plan to breastfeed
  • Take medication for high blood pressure, as well as medication for erectile dysfunction (phosphodiesterase type 5 inhibitor)


Every medication comes with side effects. Doxazosin is considered a low-risk, less potent medication. 

Read the prescription label that comes with your medication package, and ask your healthcare providers if you have any queries. 

Then, follow their advice and make sure you are taking the medication in the correct ways.

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  1. Kim, J., & Nguyen, H. (2022). Doxazosin. In StatPearls. StatPearls Publishing.
  2. U.S. Food and Drug Administration. (2021, Jun 23). CARDURA
  3. National Health System. (2022, Mar 2). Side effects of doxazosin
  4. Barrios, V., Escobar, C., Tomás, J. P., Calderon, A., & Echarri, R. (2009). Doxazosin and heart failure: to be or not to be. Journal of hypertension, 27(2), 433-434.
  5. Antihypertensive, T., & Coordinators for the ALLHAT Collaborative Research Group. (2002). Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel blocker vs diuretic: the Anti-hypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). Jama, 288(23), 2981-2997.

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