Tamsulosin side effects: things to consider

If you've been prescribed tamsulosin (brand name Flomax) for benign prostatic hyperplasia (BPH), you might want to know more about potential tamsulosin side effects. Although studies show that tamsulosin is a safe and effective medication, all drugs can have the potential for adverse effects. Some tamsulosin side effects include dizziness, headaches, priapism, low blood pressure, and more. Continue reading to learn more about the medication. 

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Tamsulosin (brand name Flomax) is part of a class of medications known as alpha-blockers (α-blockers). The medication is FDA-approved to treat benign prostatic hyperplasia (BPH), also known as an enlarged prostate. This is a common condition that affects about half of all men between the ages of 51 and 60 and over 70% of men older than 60.

The prostate gland is located at the base of the bladder and surrounds the ureter (the tube that carries urine from the bladder out of the body via the penis). As the prostate gets larger, it can put pressure on the urethra, leading to lower urinary tract symptoms (LUTS). A classic symptom of BPH is needing to pee more often, especially at night. 

Other symptoms of BPH include difficulty starting urination, weak urine flow, straining when urinating, and starting/stopping frequently during urination. Tamsulosin helps relax the muscles of the prostate and bladder. This can allow the urethra to expand and improve the flow of urine, alleviating urinary symptoms caused by an enlarged prostate. 

Other examples of alpha blockers include prazosin (brand name Minipress), silodosin (brand name Rapaflo), alfuzosin (brand name Uroxatral), terazosin (brand name Hytrin), and doxazosin (brand name Cardura).

Common side effects of tamsulosin include:

• Dizziness or lightheadedness

• Headache

• Runny nose, stuffy nose, or other "common cold" symptoms

• Abnormal ejaculation, such as ejaculation failure

• Drowsiness

• Diarrhea

• Intraoperative floppy iris syndrome (can occur during cataract surgery or glaucoma surgery) 

Serious side effects of tamsulosin can include:

• Chest pain (angina)

• Low blood pressure or fainting (syncope), especially when standing from a sitting position (also known as orthostatic hypotension)

• A severe allergic reaction with skin rash, swelling, and trouble breathing; if you have a history of an allergy to sulfonamide ("sulfa") drugs, you may also have an allergic reaction to tamsulosin 

Tamsulosin also has potential drug interactions with several different medications, including PDE5 inhibitors used to treat erectile dysfunction and drugs that block the liver enzymes needed to break down tamsulosin. Let your healthcare provider know if you’re taking any other medications, whether over-the-counter or prescription drugs.

In the last few years, there’s been some controversy about whether tamsulosin increases the risk of dementia in the elderly.

A 2018 study examined Medicare data about men taking tamsulosin over a period of six years (2006-2012). The researchers found that taking tamsulosin may increase the risk of developing dementia.

However, a 2019 study pointed out several limitations of the study mentioned above. Using records from the National Health Insurance Database, South Korean researchers looked for a connection between α-blocker use and dementia inKorean adults with BPH between 2011 and 2017—they didn't find one. The authors concluded that benign prostatic hyperplasia medication is not associated with a risk of dementia. It does not seem that tamsulosin definitively increases the risk of dementia in the elderly, but more research is needed. 

A study looking at the long-term safety and effectiveness of tamsulosin in men who took tamsulosin for six years found that some of the most common adverse effects included infection, accidental injury, runny nose, pain, and sore throat. Other reported side effects included abnormal ejaculation, syncope, and orthostatic hypotension. Interestingly, participants’ side effects declined over the six-year period, with the highest levels occurring in the first two years of treatment.

In summary, people taking tamsulosin to treat BPH urinary symptoms continued to have safe and well-tolerated relief of their symptoms for up to six years.  

If you stop taking tamsulosin (brand name Flomax) for a few days, talk with a healthcare provider before starting again. Your provider may have you restart at the lowest dose to prevent side effects.

If you experience any symptoms of BPH, it’s important to make an appointment with your healthcare provider as soon as possible. They will help you develop a safe and effective treatment plan to relieve your symptoms.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

February 17, 2023

Written by

Michael Martin

Fact checked by

Chimene Richa, MD

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About the medical reviewer

Chimene Richa, MD

Dr. Richa is a board-certified Ophthalmologist and medical writer for Ro.