Tamsulosin

Brand Names: Flomax

Prescription Needed: Yes

What is this drug used for?

Tamsulosin is primarily used in men to treat the symptoms of benign prostatic hyperplasia (enlarged prostate). It works by relaxing the muscles around the prostate gland and bladder allowing urine to pass more freely.

Is there any reason not to take this drug?

You should not take this drug if you are allergic to tamsulosin. If you are undergoing cataract surgery tell your doctor you are taking this medication. Tell your doctor if you have or have ever had:

  • low or high blood pressure
  • problems with dizziness
  • severe problems with your liver
  • cancer of the prostate

What about possible side effects?

Some common side effects are:

  • difficulty ejaculating
  • feeling dizzy and off-balance
  • feeling drowsy
  • itchy stuffy or runny nose

These side effects may be related to dose the use of other medications and other factors (e.g. older age other medical conditions). As well some of these side effects may go away with time. Talk to your doctor or pharmacist about whether you have any risk factors that may make you more sensitive to these side effects. Contact your doctor if these symptoms continue or become worse.

Other less common side effects include:

  • rash
  • nausea or diarrhea
  • feeling pain aches or weakness in the joints or muscles
  • very rare reports of a condition called priapism (painful erection of the penis that lasts for hours) - contact your doctor immediately


This is not a complete list of side effects. If you are concerned about these or other unusual symptoms while taking this medication ask your doctor and/or pharmacist for more information and advice.

What if I am taking other drugs?

Always provide your doctor with a list of all other drugs you are taking (including over-the-counter medications and herbal/natural products) as they may interact with and/or may change the safety or effectiveness of either drug. Tell your doctor specifically if you are taking any of the following as he/she may need to make changes or monitor you more closely:

  • other medications to treat high blood pressure:
    • may increase your chances for experiencing low blood pressure - e.g. beta blockers water pills calcium channel blocker
  • prazosin dosazosin terazosin - these medications should not be used together with tamsulosin
  • medications for erectile dysfunction such as sildenafil vardenafil or tadalifil - may increase your chance of experiencing low blood pressure
  • cimetidine - may increase the amount of tamsulosin in your blood
  • warfarin - interaction is unknown may need more frequent monitoring

This is not a complete list of drug interactions. Ask your doctor or pharmacist to review your list of medications.

Other information

Side effect management: When you first start to take tamsulosin it may cause your blood pressure to drop and you may feel faint or dizzy as a result.

Sit or stand up slowly while taking this medication. Contact your doctor if you continue to experience dizziness or fainting.

Use in enlarged prostate: Although you should see some improvement right away it may take some time (one to two weeks) to see the full effect of the medication on your urinary symptoms. You should continue to use the medication for persistent effect.

Tamsulosin does not cure an enlarged prostate and does not reduce its size. If it continues to increase in size symptoms may worsen over time and other treatment may be necessary.

How to take: Tamsulosin comes in capsules. The recommended initial daily dosage is 0.4-0.8 mg daily depending on what your doctor has prescribed. Although it may be best to take tamsulosin about 30 minutes after breakfast at the same time each day the most important thing is that it is taken the same way every day. Otherwise you may get different amounts of the drug into the body.

Children: Not prescribed.

Seniors: May be more sensitive to effects. Lower dose may be necessary especially at the start of therapy.

Pregnant women: Not prescribed.

Women who are nursing: Not prescribed.

People who drive or operate machinery: Should not do so until they know how this drug affects them personally. May cause dizziness or drowsiness.

Alcohol: Excessive alcohol can lower your blood pressure so you need to be careful when being treated with tamsulosin. If you drink always drink in moderation.

Overdose: If you have taken a large overdose and/or notice any unusual symptoms i.e. dizziness rapid pulse or drowsiness see a doctor.

Stopping the drug: Do not stop taking this drug until you have spoken to your doctor. It takes time to see an effect. Once you stop taking the medication your difficulty with urinating will likely return.

If you miss a dose: Take it as soon as you remember and skip the next regular dose if it is scheduled within four hours. Never take a double dose.

Storage conditions: Closed container; cool dry location away from excess moisture (not in the bathroom) and light; always out of reach of children.

Dietary precautions: No specific recommendations.