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  1. Tamsulosin is used to treat the symptoms of benign prostatic hyperplasia (BPH).
  2. This drug comes as a capsule that you take by mouth.
  3. Tamsulosin is available as the brand-name drug Flomax. It’s also available as a generic drug.

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Important Information

Rarely, tamsulosin can cause priapism. This is a persistent, painful erection that isn’t related to sexual activity. If you have priapism, contact your doctor right away. If priapism isn’t treated, it could lead to permanent impotence (not being able to have an erection).

Skin reactions
Though rare, this drug can cause severe skin reactions, including a serious condition called Stevens-Johnson syndrome. These skin reactions can cause raised welts, facial swelling, fever, and trouble breathing. See a doctor right away or call 9-1-1 if you have signs of a sudden or severe skin reaction after taking this drug.

Intraoperative floppy iris syndrome (IFIS)
IFIS is a complication that can occur during surgery for cataracts or glaucoma. Although rare, this problem has been reported with patients taking tamsulosin. If you need to have cataract or glaucoma surgery, be sure to tell your doctor or surgeon that you’re taking this drug.

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What is Tamsulosin?

Tamsulosin is a prescription drug. It comes as a capsule you take by mouth.

Tamsulosin is available as the brand-name drug Flomax. It’s also available as a generic drug. Generic drugs usually cost less. In some cases, they may not be available in every strength or form as the brand-name version.

This drug may be used as part of a combination therapy. That means you may need to take it with other drugs.

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Why it's used

Tamsulosin is used to treat the symptoms of benign prostatic hyperplasia (BPH). BPH is a condition that can occur in men. With BPH, the prostate is enlarged but isn’t cancerous. Symptoms of BPH include trouble urinating, and a frequent or urgent need to urinate that often occurs at night.

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How it works

Tamsulosin belongs to a class of drugs called alpha-adrenergic blockers. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

Tamsulosin works by relaxing the muscles in your bladder and prostate. This helps improve the flow of your urine.

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More common side effects

The more common side effects that occur with tamsulosin include:

  • headache
  • dizziness
  • runny nose
  • diarrhea
  • cough
  • decreased semen
  • loss of energy or muscle strength
  • sore throat or trouble swallowing
  • back or chest pain

If these side effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

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Serious side effects

Call your doctor right away if you have serious side effects. Call 9-1-1 if your symptoms feel life threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • abnormal ejaculation
  • priapism (painful, long-lasting erection)
  • flu-like symptoms
  • blurred vision
  • low blood pressure when changing positions that causes you to feel lightheaded, faint, or dizzy
  • allergic reaction, with trouble breathing, fever, swelling of your throat or tongue, rash, itching, or hives

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You asked, we answered

  • How long does it take tamsulosin to work?
  • Most people notice symptoms of BPH starting to improve within a week of taking tamsulosin. This is the time it takes for the drug to build up in your body to a level that works. If urinating doesn’t get easier for you or you don’t have fewer urges to urinate within 2 weeks after starting this drug, tell your doctor. Your doctor may need to change your dosage or have you take another drug.

    - Healthline Pharmacist Review Team

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Tamsulosin may interact with other medications

Tamsulosin can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Medications that might interact with this drug

Acid-blocking drugs

  • cimetidine

Taking cimetidine with tamsulosin can increase the levels of tamsulosin in your body. This raises your risk of side effects from tamsulosin.


  • erythromycin

Taking this drug with tamsulosin could increase the levels of tamsulosin in your body. This would raise your risk of side effects from tamsulosin.

Antidepressants (SSRIs)

  • paroxetine

Taking paroxetine with tamsulosin can increase the levels of tamsulosin in your body. This raises your risk of side effects from tamsulosin.


  • terbinafine
  • ketoconazole

Taking these drugs with tamsulosin can increase the levels of tamsulosin in your body. This raises your risk of side effects from tamsulosin.

Erectile dysfunction drugs

  • sildenafil
  • tadalafil
  • vardenafil

Taking these drugs with tamsulosin can cause very low blood pressure.

Other drugs

  • alpha-blockers, including:
    • doxazosin
    • prazosin

Taking these drugs with tamsulosin can cause very low blood pressure.

Other benign prostatic hyperplasia drugs

  • alfuzosin

Taking this drug with tamsulosin could worsen low blood pressure, a side effect of tamsulosin. Symptoms can include dizziness, fainting, and falls.

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Tamsulosin Warnings

Tamsulosin can cause severe allergic reactions, such as a serious condition called Stevens-Johnson syndrome. These reactions can cause symptoms including:

  • trouble breathing
  • swelling of your throat or tongue
  • rash, itching, hives

If you have an allergic reaction, call your doctor or local poison control center right away. If your symptoms are severe, call 9-1-1 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it or to sulfa. Sulfa is an ingredient found in certain drugs. Taking it again could be fatal (cause death). Tell your doctor if you’ve had a serious or life-threatening allergic reaction to sulfa.

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All possible dosages and forms may not be included here. Your doctor will tell you what dosage is right for you. Your dosage, form, and how often you take the drug will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

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What are you taking this medication for?

Benign prostatic hyperplasia (BPH)

Brand: Flomax
Form: Oral capsule
Strength: 0.4 mg

Generic: Tamsulosin
Form: Oral capsule
Strengths: 0.4 mg

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Adult Dosage (ages 18-64 years)

The typical dose for tamsulosin is one 0.4-mg capsule. Take it 30 minutes after a meal, at the same time each day.

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Senior Dosage (ages 65 years and older)

Your body may process this drug more slowly. Your doctor may start you on a lowered dose so that levels of the drug don’t build up too high in your body. High levels of this drug in your body can be dangerous.

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Pharmacist's Advice
Tamsulosin comes with risks if you don’t take it as prescribed.

If you stop taking the drug suddenly or don’t take it at all
Your BPH symptoms will not improve. If you stop taking this drug for several days, talk to your doctor before starting again.

If you miss doses or don’t take the drug on schedule
Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much
If you think you have taken too much tamsulosin, call a poison control center or go to your nearest emergency department right away. Taking too much of this drug can cause low blood pressure. This can be dangerous.

What to do if you miss a dose
Take your dose as soon as you remember. But if you remember just a few hours before your next scheduled dose, take only one dose. Never try to catch up by taking two doses at once. This could result in dangerous side effects.

How to tell if the drug is working
You should see a decrease in the symptoms of BPH. You may need to urinate less often, have less urgency to urinate, or have a stronger urine stream.

Tamsulosin is used for long-term treatment.

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Important considerations for taking this drug

You should take this drug 30 minutes after a meal

Don’t crush or cut the capsule

Store this drug carefully

  • Keep this drug at room temperature from 59–86°F (15–30°C).
  • Don’t freeze this medication.
  • Keep this drug away from light.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

This medication is refillable

When traveling with your medication:

  • Always carry your medication with you, such as in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t hurt your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled box with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

You may need to be screened for prostate cancer
Benign prostatic hyperplasia (BPH) can occur with more serious conditions such as prostate cancer. Before starting treatment with tamsulosin, talk to your doctor about being screened for prostate cancer.

You will have regular checkups with your doctor
During these visits, your doctor will check whether your signs and symptoms of BPH have improved.

Part 21 of 21

Are there any alternatives?

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other options that may work for you.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.