Tamsulosin

Tamsulosin

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Systematic (IUPAC) name
(R)-5-(2-(2-(2-ethoxyphenoxy)ethylamino)propyl)- 2-methoxybenzenesulfonamide
Clinical data
Pregnancy category	B2 (Aust)
Routes of administration	oral
Legal status
Legal status	Schedule 4 (Aust) P (UK)
Pharmacokinetic data
Bioavailability	100% (oral)
Metabolism	hepatic
Biological half-life	9–13 hours
Excretion	76% renal
Identifiers
CAS Number	106133-20-4
ATC code	G04CA02 (WHO)
PubChem	CID 129211
IUPHAR/BPS	488
DrugBank	APRD00036
ChemSpider	114457
Chemical data
Formula	C20H28N2O5S
Molar mass	408.51[[]]
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Tamsulosin (rINN) (pronounced /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 and Urimax, though generic non-modified release capsules are still approved and marketed in many countries, such as Canada. The U.S. patent for Flomax expired October 2009.

In Egypt and Iceland it is marketed under the trade Omnic by Astellas pharma europe.

Mechanism

Main article: Alpha blocker

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.

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.

Tamsulosin has also affected the sexual function in men. Tamsulosin can cause males to experience retrograde ejaculation. 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 have recently demonstrated that treatment with the combination of Avodart and tamsulosin provides superior symptom benefits compared with either monotherapy.

External links

• Tamsulosin – information from USP DI Advice for the Patient
• Flomax (drugs.com) – U.S. product information
• Flomax (Official Site) – Official Site

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