by Nicole Evans M.D.

Created on: December 05, 2009   Last Updated: June 03, 2010

Flomax is a medication commonly prescribed for men who have an enlarged prostate, a condition known as benign prostatic hypertrophy. An enlarged prostate can cause urinary retention, difficulty starting the urine stream and nocturia (frequent urination during the night).  Flomax may lessen these symptoms and is particularly useful for men with urinary retention.

Flomax, generically named Tamsulosin, works by blocking alpha-adrenergic receptors in the smooth muscle of the prostate.  When Flomax blocks these receptors the prostatic smooth muscle relaxes resulting in improved urine flow and decreased BPH symptoms.

As with most medications, Flomax has many side effects and contraindications, ranging from minor symptoms such as headache and nausea to potentially dangerous conditions such as severe allergic reactions  and syncope (fainting).

The most common Flomax side effects occur in over 10% of men who use this medication.  These side effects include headache, dizziness, abnormal ejaculation, rhinitis or inflamed runny nose and infections.

Other side effects of Flomax require particular attention, though they are less common, because they are potentially dangerous and in some cases have resulted in significant harm to patients.  These include:

*Chest pain: 4% of men may experience chest pain on Flomax. Discontinue Flomax if symptoms of angina (chest pain) occur or worsen.

*Orthostatic hypotension and syncope (passing out): 6 % to 19% of men may experience these side effects of Flomax. Orthostatic hypotension is a drop in blood pressure when going from laying down or sitting to standing. Flomax may cause orthostatic hypotension and syncope (fainting) within 4 to 8 hours of the first dose. These symptoms are also likely to occur if the dosage is rapidly increased, if another antihypertensive drug is started, or if Viagra or Cialis is started. Older patients may be more sensitive to the orthostatic hypotension caused by Flomax.

*Priapism: Priapism is an erection sustained for a dangerously long time. Flomax has been associated with priapism, though this is a rare side effect.

*Floppy iris syndrome: Cataract surgery patients who were on or were previously treated with Flomax have been observed to have a condition known as intraoperative floppy iris syndrome. However, it is not clear that Flomax causes floppy iris syndrome and there appears to be no benefit in discontinuing Flomax prior to surgery.

The less common adverse effects that men taking Flomax may experience include:

* Somnolence or sleepiness (3% to 4% of men), insomnia (1% to 2% of men), vertigo (1% of men)

* Libido, or sex drive, decreased (1% to 2% of men)

* Palpitations or irregular heart beat

* Diarrhea (4% to 6% of men), nausea (3% to 4% of men), tooth disorders (1% to 2% of men), vomiting or constipation (rare)

* Weakness (8% to 9% of men), back pain (7% to 8% of men)

* Blurred vision (2% of men)

* Pharyngitis or sore throat (5% to 6% of men), cough (3% to 5% of men), sinusitis (2% to 4% of men)

* Allergic reactions (angioedema, itching, rash, skin welts, respiratory symptoms)

Flomax has many side effects. Some of the adverse effects of Flomax may warrant discontinuing the medication. However, for many men the benefits may outweigh the risk of side effects. Individuals should work with their physician to determine if Flomax is right for them.

*Lexi-Comp Online. Lexi-drugs. 2010.

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