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Flomax Patient Tips

Written by C. Fookes, BPharm on May 22, 2017

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 is used to treat the symptoms of BPH, also referred to as an enlarged prostate gland.


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).
  • 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.
  • Rarely, may cause a reaction in people with a sulfa allergy.

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.
  • Do not crush, chew or open Flomax capsules.
  • Stand up slowly and not in an area where injury is likely if you fall over. Talk to your doctor if you are experiencing a significant drop in blood pressure when you stand 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.
  • Since BPH and prostate cancer can coexist, talk to your doctor about screening for prostate cancer.

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 (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.

  • Disclaimer: Every effort has been made to ensure that this information is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. This drug information does not endorse drugs, diagnose patients or recommend therapy. It is an informational resource designed as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of this information. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2017 Revision Date: 2017-05-23 00:52:16