Tamsulosin

Tamsulosin (rINN) ( /tæmˈsuːlɵsɨn/ or /tæmsʉˈloʊsɨn/) is an α_1a-selective alpha blocker used in the symptomatic treatment of benign prostatic hyperplasia (BPH). Tamsulosin was developed by Yamanouchi Pharmaceuticals (now part of Astellas Pharma) and is marketed by various companies under licence, including Boehringer-Ingelheim and CSL. Tamsulosin hydrochloride extended-release capsules are marketed under the trade names Flomax, Flomaxtra, Contiflo XL, and Urimax, though generic non-modified release capsules are still approved and marketed in many countries, such as Canada. In Colombia (South America) it is marketed under Uripur from Laboratorios Bussié, beside it is marketed under Harnal D in some places.^[1] The U.S. patent for Flomax expired in October 2009. The U.S. Food and Drug Administration (FDA) approved generic Flomax in March 2010.^[2]

In Egypt^[3] Italy and Iceland it is marketed under the trade Omnic by Astellas Pharma Europe.

Mechanism

Tamsulosin is a selective α₁ receptor antagonist that has preferential selectivity for the α_1A receptor in the prostate versus the α_1B receptor in the blood vessels.^[4]

Clinical uses

Tamsulosin is primarily used for benign prostatic hyperplasia, but is sometimes used for the passage of kidney stones by the same mechanism of smooth muscle relaxation via alpha antagonism.

Adverse effects

Two ADRs (Adverse Drug Reactions) have been reported:

• Immunologic: It contains a sulfa moiety, thus causing typical reactions to sulfa drugs.
• Ophthalmologic: Patients taking tamsulosin are prone to a complication known as floppy iris syndrome during cataract surgery. Adverse outcomes of the surgery are greatly reduced by the surgeon's prior knowledge of the patient's history with this drug, and thus having the option of alternative techniques.^[5]

Tamsulosin has also affected the sexual function in men. Tamsulosin can cause males to experience retrograde ejaculation.^[6] In males, retrograde ejaculation occurs when the fluid to be ejaculated, which would normally exit the body via the urethra, is redirected to the urinary bladder. Normally, the sphincter of the bladder contracts and the ejaculate goes to the urethra, the area of least pressure. In retrograde ejaculation, this sphincter does not function properly.

Occasionally, tamsulosin can cause a drop in blood pressure, rarely resulting in dizziness or fainting. Other reported side effects include headache, dizziness, nasal congestion, and palpitations.

Clinical comparison

Although prostate specific, it does not have the prostate apoptotic effects of other alpha-blockers such as doxazosin and terazosin.

Use in combination therapy

The results of the CombAT (Combination of Avodart and Tamsulosin) trial in 2008 demonstrated that treatment with the combination of dutasteride (Avodart) and tamsulosin provides greater symptom benefits compared to monotherapy with either agent alone for treatment of benign prostatic hyperplasia. ^[7]

References

Notes

External links

• Tamsulosin – information from USP DI Advice for the Patient
• Flomax (drugs.com) – U.S. product information
• Product label U.S. Food and Drug Administration (FDA)
• Flomax (Official Site) – Official Site