Tamsulosin (Flomax) – Side Effects, Interactions, Uses, Dosage, Warnings

Tamsulosin is an alpha-blocker that is used to improve urination in men with benign prostatic hyperplasia (enlarged prostate).

Tamsulosin is not approved for use in women or children.

Tamsulosin may also be used for purposes not listed in this medication guide.


What is Tamsulosin (Flomax) used for?

  • Benign Prostatic Hyperplasia


What is the most important information I should know about Tamsulosin (Flomax)?

You should not use tamsulosin if you are allergic to it.

Tell your doctor if you have ever had:

  • liver or kidney disease;
  • prostate cancer;
  • low blood pressure; or
  • an allergy to sulfa drugs.

Tamsulosin can affect your pupils. If you have cataract surgery, tell your surgeon ahead of time that you use this medicine.

Tamsulosin is not for use in women, and the effects of this medicine during pregnancy or in breastfeeding women are unknown.

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Side Effects

What are the side effects of Tamsulosin (Flomax)?

Get emergency medical help if you have signs of an allergic reaction (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).

Stop using tamsulosin and call your doctor at once if you have:

  • a light-headed feeling, like you might pass out; or
  • penis erection that is painful or lasts 4 hours or longer.

Tamsulosin lowers blood pressure and may cause dizziness or fainting, especially when you first start taking it. You may feel very dizzy when you first wake up. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

Common side effects may include:

  • abnormal ejaculation, decreased amount of semen;
  • dizziness, drowsiness, weakness;
  • runny nose, cough;
  • back pain, chest pain;
  • nausea, diarrhea;
  • tooth problems;
  • blurred vision;
  • sleep problems (insomnia); or
  • decreased interest in sex.

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.

Pregnancy & Breastfeeding

Can I take Tamsulosin (Flomax) if I’m pregnant or breastfeeding?

Tamsulosin is not for use in women, and the effects of this medicine during pregnancy or in breastfeeding women are unknown.


What drugs and food should I avoid while taking Tamsulosin (Flomax)?

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.

Dosage Guidelines & Tips

How to take Tamsulosin (Flomax)?

Use Tamsulosin (Flomax) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Your doctor may test your prostate specific antigen (PSA) to check for prostate cancer before you take tamsulosin.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Tamsulosin is usually taken once a day, approximately 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.

Some things can cause your blood pressure to get too low. This includes vomiting, diarrhea, or heavy sweating. Call your doctor if you are sick with vomiting or diarrhea.

Store at room temperature away from moisture and heat.

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

What should I do if I missed a dose of Tamsulosin (Flomax)?

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 miss your doses for several days in a row, talk with your doctor before restarting the medication.

Overdose Signs

What happens if I overdose on Tamsulosin (Flomax)?

If you think you or someone else may have overdosed on: Tamsulosin (Flomax),  call your doctor or the Poison Control center

(800) 222-1222

If someone collapses or isn't breathing after taking Tamsulosin (Flomax), call 911



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