Tamsulosin

Tamsulosin

Systematic (IUPAC) name
(R)-5-(2-{[2-(2-ethoxyphenoxy)ethyl]amino}propyl)-2-methoxybenzene-1-sulfonamide
Clinical data
Trade names	Flomax
AHFS/Drugs.com	monograph
MedlinePlus	a698012
Licence data	US FDA:link
Pregnancy cat.	B2 (AU) B (US)
Legal status	Prescription Only (S4) (AU) POM (UK) ℞-only (US)
Routes	oral
Pharmacokinetic data
Bioavailability	100% (oral)
Metabolism	hepatic
Half-life	9–13 hours
Excretion	76% renal
Identifiers
CAS number	106133-20-4 Y
ATC code	G04CA02
PubChem	CID 129211
IUPHAR ligand	488
DrugBank	DB00706
ChemSpider	114457 Y
UNII	G3P28OML5I Y
KEGG	D08560 Y
ChEBI	CHEBI:9398 Y
ChEMBL	CHEMBL836 Y
Chemical data
Formula	C20H28N2O5S
Mol. mass	408.51
SMILES	eMolecules & PubChem
InChI InChI=1S/C20H28N2O5S/c1-4-26-17-7-5-6-8-18(17)27-12-11-22-15(2)13-16-9-10-19(25-3)20(14-16)28(21,23)24/h5-10,14-15,22H,4,11-13H2,1-3H3,(H2,21,23,24)/t15-/m1/s1 Y Key:DRHKJLXJIQTDTD-OAHLLOKOSA-N Y
Y (what is this?)  (verify)

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 was first marketed in 1996 under the trade name Flomax. It is now 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, although generic, non-modified-release capsules are still approved and marketed in many countries (such as Canada). In Mexico it is marketed as Secotex and as Harnal D in Japan and Indonesia. In Egypt, Italy and Iceland, it is marketed under the trade name Omnic by Astellas Pharma Europe.

The U.S. patent for Flomax expired in October 2009. The U.S. Food and Drug Administration (FDA) approved generic Flomax in March 2010.

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.

When alpha 1 receptors in the bladder neck and the prostate are blocked, this causes a relaxation in smooth muscle and therefore less resistance to urinary flow. Due to this the pain associated with BPH can be reduced.

Clinical uses

Flomax 0.4 MG Oral Capsule

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.^{citation needed}

Adverse effects

Two ADRs (Adverse Drug Reactions) have been reported:

• Immunologic: It contains a sulfa moiety, thus causing typical reactions to sulfa drugs.^{citation needed}
• 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.^{citation needed} Other reported side effects include headache, dizziness, nasal congestion, and palpitations.^{citation needed}

Clinical comparison

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

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. This combination can be useful as it can take up to six months for any symptomatic relief to be found by 5-alpha-reductase inhibitors such as dutasteride compared to alpha-1 receptor blockers which can provide relief in some cases within 48 hours.

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