Clinical data
Pronunciation /tæmˈsləsən/[1]
Trade names Flomax, Omnic
AHFS/Drugs.com Monograph
MedlinePlus a698012
License data
  • AU: B2
  • US: B (No risk in non-human studies)
Routes of
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
CAS Number 106133-20-4 YesY
PubChem (CID) 129211
DrugBank DB00706 YesY
ChemSpider 114457 YesY
KEGG D08560 YesY
ECHA InfoCard 100.109.780
Chemical and physical data
Formula C20H28N2O5S
Molar mass 408.51
3D model (Jmol) Interactive image

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 α1a 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

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]


Main article: Alpha blocker

Tamsulosin is a selective α1 receptor antagonist that has preferential selectivity for the α1A receptor in the prostate versus the α1B 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).


  1. "Tamsulosin". Merriam-Webster Dictionary.
  2. 1 2 Wang, RC; Smith-Bindman, R; Whitaker, E; Neilson, J; Allen, IE; Stoller, ML; Fahimi, J (7 September 2016). "Effect of Tamsulosin on Stone Passage for Ureteral Stones: A Systematic Review and Meta-analysis.". Annals of emergency medicine. PMID 27616037.
  3. "Benign prostatic hyperplasia (BPH)". Mayo Clinic.
  4. "Flomax – Big Patent Expirations of 2010". February 10, 2010. Retrieved 14 January 2012.
  5. "FDA Approves First Generic Tamsulosin to Treat Enlarged Prostate Gland" (Press release). U.S. Food and Drug Administration (FDA). March 2, 2010.
  6. "Tamsulosin Aids Stone Expulsion". Renal and Urology News.
  7. "Study Shows Use of Tamsulosin or Nifedipine Helps Patients to Clear Ureteral Stone Fragments Faster and Reduces Rate of Recurrence".
  8. Lucas MG, Stephenson TP, Nargund V (February 2005). "Tamsulosin in the management of patients in acute urinary retention from benign prostatic hyperplasia". BJU Int. 95 (3): 354–7. doi:10.1111/j.1464-410X.2005.05299.x. PMID 15679793.
  9. Jeong IG, You D, Yoon JH, et al. (February 2014). "Impact of tamsulosin on urinary retention following early catheter removal after robot-assisted laparoscopic radical prostatectomy: A prospective randomized controlled trial". Int. J. Urol. 21 (2): 164–8. doi:10.1111/iju.12225. PMID 23906190.
  10. PharmacistAnswers Tamsulosin & Catheterization Retrieved February 12, 2014.
  11. "Tamsulosin (Oral Route) - Before Using". Mayo Clinic. Retrieved 5 June 2015.
  12. Medscape, Good Cataract Surgery Outcomes Possible in Intraoperative Floppy Iris Syndrome Due to Tamsulosin.
  13. Bird, ST; Delaney, JA; Brophy, JM; Etminan, M; Skeldon, SC; Hartzema, AG (Nov 5, 2013). "Tamsulosin treatment for benign prostatic hyperplasia and risk of severe hypotension in men aged 40-85 years in the United States: risk window analyses using between and within patient methodology.". BMJ (Clinical research ed.). 347: f6320. doi:10.1136/bmj.f6320. PMID 24192967.
  14. Ramirez, J (Nov 5, 2013). "Severe hypotension associated with α blocker tamsulosin.". BMJ (Clinical research ed.). 347: f6492. doi:10.1136/bmj.f6492. PMID 24192968.
  15. "Tamsulosin Side Effects". Drugs.com. Retrieved 2011-04-27
  16. Roehrborn CG, Siami P, Barkin J, et al. (February 2008). "The effects of dutasteride, tamsulosin and combination therapy on lower urinary tract symptoms in men with benign prostatic hyperplasia and prostatic enlargement: 2-year results from the CombAT study". J. Urol. 179 (2): 616–21; discussion 621. doi:10.1016/j.juro.2007.09.084. PMID 18082216.
  17. Approval letter
  18. Australian Medicines Handbook
  19. Shen, Howard (2008). Illustrated Pharmacology Memory Cards: PharMnemonics. Minireview. p. 13. ISBN 1-59541-101-1.
  20. . doi:10.1136/bmj.f6320. Missing or empty |title= (help)
  21. Dr. Sandro Magnanelli; Dr.ssa Ada Maria Vetere. "Pradif 0,4 Mg Capsule Rigide A Rilascio Prolungato". Torrinomedica.it. Retrieved 15 November 2012.
  22. "Drugs.com Database".
  23. "Novartis hits Astellas with transplant drug generic". Reuters. 11 August 2009. Retrieved 11 August 2009.

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