Tamsulosin

Tamsulosin

Clinical data
Pronunciation	/tæmˈsuːləsən/[1]
Trade names	Flomax, Omnic
AHFS/Drugs.com	Monograph
MedlinePlus	a698012
License data	US FDA: Tamsulosin
Pregnancy category	AU: B2 US: B (No risk in non-human studies)
Routes of administration	by mouth
ATC code	G04CA02 (WHO)
Legal status
Legal status	AU: S4 (Prescription only) UK: POM (Prescription only) US: ℞-only
Pharmacokinetic data
Bioavailability	100% (by mouth)
Metabolism	hepatic
Biological half-life	9–13 hours
Excretion	76% kidney
Identifiers
IUPAC name (R)-5-(2-{[2-(2-Ethoxyphenoxy)ethyl]amino}propyl)-2-methoxybenzene-1-sulfonamide
CAS Number	106133-20-4 Y
PubChem (CID)	129211
IUPHAR/BPS	488
DrugBank	DB00706 Y
ChemSpider	114457 Y
UNII	G3P28OML5I Y
KEGG	D08560 Y
ChEBI	CHEBI:9398 Y
ChEMBL	CHEMBL836 Y
ECHA InfoCard	100.109.780
Chemical and physical data
Formula	C20H28N2O5S
Molar mass	408.51
3D model (Jmol)	Interactive image
SMILES CCOc1ccccc1OCCN[C@@H](C)Cc1ccc(OC)c(c1)S(=O)(=O)N
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
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Tamsulosin, sold under the trade name Flomax, is a medication used to treat symptomatic benign prostatic hyperplasia (BPH), help with the passage of kidney stones,^[2] and for urinary retention along with other measures.

Tamsulosin, and other medications in the class called alpha blockers, work by relaxing bladder neck muscles and muscle fibers in the prostate itself and make it easier to urinate.^[3] It is an α_1a adrenergic receptor antagonist.

Tamsulosin was developed by Yamanouchi Pharmaceuticals (now part of Astellas Pharma) and was first marketed in 1996. The U.S. patent expired in October 2009.^[4] The U.S. Food and Drug Administration (FDA) approved generics in March 2010.^[5]

Medical uses

Flomax 0.4 MG Oral Capsule

Tamsulosin is primarily used for benign prostatic hyperplasia and to help with the passage of kidney stones.^[6][7] Tamsulosin, however, appears to be effective only for stones over 4 mm and less than 10 mm in size.^[2]

Tamsulosin is also used as an add on treatment for acute urinary retention. People may void more successfully after catheter removal if they are taking tamsulosin. People taking tamsulosin are also less likely to need re-catheterization.^[8][9][10]

Adverse effects

• Immunologic: Higher risk of allergic reaction in those with sulfa allergies.^[11]
• 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.^[12]
• Severe hypotension.^[13][14]
• Congestive Heart Failure:
• Urology Textbook  : Cardiac Contraindications: Hypotension, mechanical heart failure (valvular, pulmonary embolism, pericarditis), congestive heart failure.
• American Heart Association: article, Drugs That May Cause or Exacerbate Heart Failure, A Scientific Statement From the American Heart Association, (Urological Medications, α₁-Blockers).

Tamsulosin has also affected sexual function in men. It can cause males to experience retrograde ejaculation.^[15] 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 bladder sphincter contracts and the ejaculate goes to the urethra, the area of least pressure. In retrograde ejaculation, this sphincter does not function properly. This side effect can be mitigated by exercising the sphincter muscle; this is done by practicing a pumping action during ejaculation and urination - some semen fluid can then be ejaculated.

Combination therapy

The results of the CombAT (combination of dutasteride and tamsulosin under the brand name Duodart) 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.^[16] The CombAT trial became the medication Jalyn. It was approved by the FDA on June 14, 2010.^[17] 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.^[18]

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.^[19]

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.

Selective action of tamsulosin in alpha 1A/D receptors is controversial and over three quarters of tamsulosin registered human studies are unpublished.^[20]

Brand names

Tamsulosin 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 Urisurge (India), Flomax, Flomaxtra, Contiflo XL, bestflo, Urimax and Pradif,^[21] 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 and as Harnal OCAS (oral controlled absorption system) in Thailand.^[22] In Egypt,^[23] Italy and Iceland, it is marketed under the trade name Omnic by Astellas Pharma Europe. The largest manufacturer of Tamsulosin, drug substance, is Synthon BV (The Netherlands).

References

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