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Flomax Patient Tips

Medically reviewed on Nov 23, 2017 by C. Fookes, BPharm

How it works

  • Flomax is a brand (trade) name for tamsulosin. Tamsulosin works on alpha receptors to relax muscles in the neck of the bladder and the prostate. This improves urine flow and reduces the symptoms of benign prostatic hyperplasia (BPH).
  • Flomax belongs to the class of medicines known as alpha-blockers.


  • Flomax may be used to improve urine flow in men with benign prostatic hyperplasia (BPH), also referred to as an enlarged prostate gland.
  • Flomax is taken just once daily.
  • No dosage adjustment is required in people with kidney disease; however, people with end-stage renal disease have not been studied.
  • Flomax is available as a generic under the name tamsulosin.


If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • A runny nose, dizziness, headache, drowsiness, and sexual dysfunction (decreased semen production, abnormal ejaculation).
  • May cause orthostatic hypotension (a drop in blood pressure when going from sitting to a standing position). This is more likely during Flomax initiation, or when increasing the dose. Vertigo and syncope (temporary loss of consciousness) may also occur.
  • Rare cases of priapism (painful erections more than 4 hours in duration) have been reported.
  • May not be suitable for people undergoing cataract or glaucoma surgery or in those with a sulfa allergy (although reactions have rarely been reported).
  • May interact with a number of other medicines including ketoconazole and other strong inhibitors of hepatic enzymes CYP3A4 (avoid this combination), erythromycin, paroxetine, terbinafine, cimetidine, warfarin, PDE 5 inhibitors (such as sildenafil, tadalafil, and vardenafil), and other alpha adrenergic blocking agents.
  • Rarely, may cause a reaction in people with a sulfa allergy.
  • Flomax capsules are not intended to be used to lower blood pressure.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

Bottom Line

Flomax restores urine flow in men with BPH but may cause a drop in blood pressure when going from a sitting to a standing position.


  • Administer at the same time each day, half an hour after a meal.
  • Take exactly as directed by your doctor. Do not increase or decrease the dosage of Flomax without his or her advice.
  • Do not crush, chew or open Flomax capsules.
  • Flomax may make you feel dizzy, especially when going from a lying down or sitting position to standing. Stand up slowly and not in an area where an injury is likely if you fall over. Remove any potential fall hazards (such as loose rugs) from your home. Talk to your doctor if you constantly experience dizziness when standing up.
  • May cause dizziness and affect your ability to drive or operate machinery. Do not drive or operate machinery until you know how Flomax affects you. Alcohol may enhance dizziness.
  • Since BPH and prostate cancer can coexist, talk to your doctor about screening for prostate cancer.
  • Talk to a doctor or pharmacist before you take any other medications with Flomax, including those bought over-the-counter, because some may not be compatible with Flomax.
  • Talk to your doctor if you experience any worrying side effects from Flomax including a sustained erection of more than a few hours duration.

Response and Effectiveness

  • Peak concentrations are reached within four to five hours when taken on an empty stomach or within six to seven hours when taken with food. May take up to five days before the full effects of Flomax on urine flow are achieved.
  • Flomax is extensively metabolized by CYP3A4 and CYP2D6 enzymes which means it can potentially interact with a number of other drugs.


Flomax (tamsulosin) [Package Insert]. Revised 01/2016. Boehringer Ingelheim Pharmaceuticals, Inc.

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

Copyright 1996-2018 Revision Date: 2017-11-23 01:28:08

Further information

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