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Tamsulosin

Brand names: Flomax

Tamsulosin relaxes the muscles in the prostate and bladder neck to make it easier to pee in men with an enlarged prostate.

Brand namesFlomax
Type of medicineAlpha blocker (prostate medicine)
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It improves urine flow but doesn't shrink the prostate.

It's sometimes used off-label to help pass kidney stones.

What it's used for

  • Symptoms of an enlarged prostate (BPH)
  • Off-label: helping pass kidney stones

How to take it

  • Take it once a day about 30 minutes after the same meal each day.
  • Swallow capsules whole.
  • If you miss several days, ask your provider before restarting; you may need to restart at a low dose.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Dizziness, especially when standing
  • Runny or stuffy nose
  • Less or no semen with ejaculation
  • Headache
Call 911An erection that's painful or lasts more than 4 hours
Call 911Swelling of the face or throat, or trouble breathing
Call your provider todayFainting

Warnings

  • Tell your eye surgeon you take (or took) it before cataract or glaucoma surgery.
  • Stand up slowly. Don't drive until you know how it affects you.
  • Tell your provider if you're allergic to sulfa drugs.

Other medicines, foods, and alcohol

  • Other alpha blockers can drop blood pressure too much.
  • Some antifungals, antibiotics, and HIV medicines raise its level.
  • Erectile dysfunction medicines can add to dizziness.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Not used in women.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.