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Generic name: tamsulosin [ tam-soo-LOE-sin ]
Brand name: Flomax
Dosage form: oral capsule (0.4 mg)
Drug class: Alpha-adrenoreceptor antagonists

Medically reviewed by Sophia Entringer, PharmD. Last updated on Apr 5, 2023.

What is tamsulosin?

Tamsulosin belongs to a class of medications called alpha blockers. It works by relaxing the muscles in the prostate and bladder so that urine can flow easily.

Tamsulosin capsules are used in men to treat the symptoms of an enlarged prostate (benign prostatic hyperplasia or BPH) which include difficulty urinating (hesitation, dribbling, weak stream, and incomplete bladder emptying), painful urination, and urinary frequency and urgency.

Tamsulosin is not approved for use in women or children.


You should not use this medication if you are allergic to tamsulosin. Do not take tamsulosin with other similar medicines such as alfuzosin (Uroxatral), doxazosin (Cardura), prazosin (Minipress), silodosin (Rapaflo), or terazosin (Hytrin).

Tamsulosin may cause dizziness or fainting, especially when you first start taking it or when you start taking it again. Be careful if you drive or do anything that requires you to be alert. Avoid standing for long periods of time or becoming overheated during exercise and in hot weather. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

If you stop taking this medicine for any reason, call your doctor before you start taking it again. You may need a dose adjustment.

Tamsulosin can affect your pupils during cataract surgery. Tell your eye surgeon ahead of time that you are using this medication. Do not stop using this medication before surgery unless your surgeon tells you to.

There are many other drugs that can interact with this medicine. Tell your doctor about all medications you use.

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Before taking this medicine

To make sure tamsulosin capsules are safe for you, tell your doctor if you have ever had:

Tamsulosin can affect your pupils. If you have cataract surgery, tell the surgeon you use this medicine .

Ask your doctor about prostate cancer screening before and while taking this medicine.

Tamsulosin is not approved for use in women.

How should I take tamsulosin?

Take tamsulosin capsules exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets..

Tamsulosin capsules are usually taken once a day, within 30 minutes after the same meal each day.

Swallow the capsule whole and do not crush, chew, break, or open it.

Your blood pressure will need to be checked often.

If you stop using this medicine, do not start it again without your doctor's advice.

Store tightly closed at room temperature, away from moisture and heat.

Dosing information

Usual Adult Dose for Benign Prostatic Hyperplasia:

0.4 mg orally once a day; the dose may be increased to 0.8 mg orally once a day in patients who fail to respond to 0.4 mg once a day within 2 to 4 weeks

-This drug should be administered approximately one-half hour following the same meal each day.

Use: Benign prostatic hyperplasia (BPH)

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

If you stop using tamsulosin for several days in a row, do not start it again without your doctor's advice.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking tamsulosin?

Avoid driving or hazardous activity until you know how this medicine will affect you. Your reactions could be impaired.

Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

Tamsulosin side effects

Get emergency medical help if you have signs of an allergic reaction to tamsulosin (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Tamsulosin may lower your blood pressure and may cause dizziness or fainting, especially when you first start taking it or your dose changes.

Tamsulosin may cause serious side effects. Stop using this medicine and call your doctor at once if you have:

  • a light-headed feeling, like you might pass out; or

  • a painful erection that lasts 4 hours or longer.

Common tamsulosin side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect tamsulosin?

Sometimes it is not safe to use certain medicines at the same time. Some drugs can affect your blood levels of other drugs you use, which may increase side effects or make the medicines less effective.

Tell your doctor about all your current medicines. Many drugs can affect tamsulosin, especially:

This list is not complete and many Other drugs may interact with tamsulosin. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Ingredients - tamsulosin capsules

Active Ingredient: tamsulosin hydrochloride
Inactive Ingredients: methacrylic acid copolymer, microcrystalline cellulose, purified water, talc, triethyl citrate, black iron oxide, FD&C Blue No. 2, gelatin, red iron oxide, titanium dioxide, yellow iron oxide and trace amounts of antifoam DC 1510, industrial methylated spirit, lecithin, n-butyl alcohol, dehydrated alcohol, isopropyl alcohol, butyl alcohol, propylene glycol, ammonium, potassium hydroxide and shellac.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use tamsulosin only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.