Sounds like 'tam-SOO-loe-sin'

Tamsulosin is used to treat symptoms of an enlarged prostate. Find out how to take it safely and possible side effects. Tamsulosin is also called Flomax.

Type of medicine Also called
  • Medicine to treat enlarged prostate 
  • Tamsulosin-Rex®
  • Flomax

What is tamsulosin?

Tamsulosin is used to treat symptoms of an enlarged prostate such as difficulty in beginning the flow of urine, weak urine flow, and the need to urinate frequently or urgently (including during the middle of the night). It works by relaxing the muscles in the prostate and part of the bladder. It does not make the prostate smaller. 


In New Zealand tamsulosin is available as capsules.

  • The dose of tamsulosin is one capsule once a day.  
  • Always take your tamsulosin exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much tamsulosin to take, how often to take it, and any special instructions.

How to take tamsulosin

  • Timing: Take tamsulosin capsules with a glass of water at the same time each day. Tamsulosin can make your feel dizzy, weak or light headed, so you may prefer to take your dose at bedtime (see dizziness and fainting below). You can take tamsulosin with or without food. To reduce your urinary symptoms, you must keep taking tamsulosin every day.
  • Alcohol: Limit drinking alcohol while you are taking tamsulosin. Alcohol can increase the chance of side effects such as feeling dizzy or faint.
  • Missed dose: If you forget your dose, take it as soon as you remember that day. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.

Side effects

Like all medicines, tamsulosin can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Dizziness and fainting

Your first dose of tamsulosin may make you feel faint, dizzy or light-headed for a few hours after taking it. To minimise the impact of this effect:

  • Take this dose at bedtime.
  • Be careful when moving from a sitting or lying position, as you are at risk of falls.
  • Stand up slowly from a sitting or lying position.
  • If you feel dizzy or faint, remain lying down until these symptoms have gone.
  • Do not drive or use tools or machines until you know how this medicine affects you.

You should also limit or avoid alcohol while you are taking tamsulosin as alcohol increases your chance of having side effects.

Other side effects

Side effects What should I do?
  • Headache
  • Try paracetamol. Check that this can be taken with any other medicines you may take.
  • Tell your doctor if troublesome.
  • Swollen feet or ankles
  • When you sit down, rest your legs on a low stool.
  • Tell your doctor if troublesome.

  • Changes in your heart beat (a pounding or racing feeling)
  • Chest pain 
  • Tell your doctor immediately or ring HealthLine.


When certain medications are taken together, an unintended reaction may occur – this is known as an interaction. Tamsulosin may interact with a few medications and herbal supplements, so check with your doctor or pharmacist.

Learn more

If you have any questions about your medicines or about the combination of medicines that you are taking, or if you are concerned about any side effects or interactions talk to your pharmacist or doctor.

The following links provide further information on tamsulosin. Be aware that websites from other countries may contain information that differs from New Zealand recommendations.

Tamsulosin Medsafe Consumer Information (NZ)
Tamsulosin Patient Info, UK

Credits: Sandra Ponen, Pharmacist. Reviewed By: Nicola Rowbottom, Pharmacist, South Canterbury Last reviewed: 09 Jan 2017