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Tamsulosin Structural Formulae.png
Tamsulosin ball-and-stick.png
Trade namesFlomax, others
  • (R)-5-(2-{[2-(2-Ethoxyphenoxy)ethyl]amino}propyl)-2-methoxybenzene-1-sulfonamide
Clinical data
Main usesBenign prostatic hyperplasia (BPH), chronic prostatitis, kidney stones[2][3][4]
Side effectsDizziness, headache, sleepiness, nausea, blurry vision, sexual problems[5][2]
  • AU: B2
  • US: B (No risk in non-human studies)
Routes of
By mouth
Defined daily dose0.4 mg[6]
External links
License data
Legal status
Bioavailability100% (by mouth)
Elimination half-life9–13 hours
Excretion76% Kidney
Chemical and physical data
Molar mass408.51 g·mol−1
3D model (JSmol)
  • CCOc1ccccc1OCCN[C@@H](C)Cc1ccc(OC)c(c1)S(=O)(=O)N
  • 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 checkY

Tamsulosin, sold under the trade name Flomax among others, is a medication used to treat symptomatic benign prostatic hyperplasia (BPH) and chronic prostatitis and to help with the passage of kidney stones.[2][3][4] The evidence for benefit with a kidney stone is better when the stone is larger.[4] It is taken by mouth.[2]

Common side effects include dizziness, headache, sleepiness, nausea, blurry vision, and sexual problems.[5][2] Other side effects may include feeling lightheaded with standing and angioedema.[5] Tamsulosin is an alpha blocker and works by relaxing muscles in the prostate.[7] Specifically it is an α1 adrenergic receptor blocker.[2]

Tamsulosin was approved for medical use in the United States in 1997.[2] It is available as a generic medication.[5] In the United States, the wholesale cost per dose is less than US$0.10 as of 2018.[8] In the United Kingdom, it costs the NHS 0.04 pounds per dose as of 2018.[5] In 2017, it was the 35th most commonly prescribed medication in the United States, with more than 20 million prescriptions.[9][10]

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.[11][12] Tamsulosin, however, appears to be effective only for stones over 4 mm and less than 10 mm in size.[4]

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 also are less likely to need re-catheterization.[13]

Tamsulosin does not decrease the overall size of the prostate in men with BPH, and is not recommended for prevention of prostate cancer.[14]


The defined daily dose is 0.4 mg by mouth.[6]

Combination therapy

The results of the CombAT (combination of dutasteride (Avodart) and tamsulosin, under the brand name Duodart) trial in 2008 demonstrated that treatment with the combination of dutasteride and tamsulosin provides greater symptom benefits compared to monotherapy with either agent alone for treatment of benign prostatic hyperplasia.[15] The CombAT trial became the medication Jalyn. It was approved by the FDA on 14 June 2010.[16] This combination can be useful because it may take up to six months for symptomatic relief to be found when using 5-alpha-reductase inhibitors such as dutasteride compared to alpha-1 receptor blockers, which can provide relief in some cases within 48 hours.[17]

Side effects

  • Immunologic: Higher risk of allergic reaction in those with sulfa allergies.[18]
  • Eyes: People 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 person's history with this drug, and thus having the option of alternative techniques.[19]
  • Severe hypotension.[20][21]
  • Persons with cardiac conditions including hypotension, mechanical heart failure (valvular, pulmonary embolism, pericarditis), and congestive heart failure should be monitored carefully while taking tamsulosin.
  • Alpha blockers, including prazosin, terazosin, doxazosin, or tamsulosin, do not appear to affect all-cause mortality in heart failure re-hospitalization in those also receiving β-blockers.[22]
  • Tamsulosin can also cause retrograde ejaculation, which occurs when semen is redirected to the urinary bladder instead of being ejaculated normally. This is because tamsulosin relaxes the muscles of the urethral sphincters, which are normally closed during ejaculation. This side effect can be mitigated by regular pelvic floor (Kegel) exercise and contracting the pelvic floor during ejaculation.[23]


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.[24]

When alpha 1 receptors in the bladder neck, the prostate, the ureter, and the urethra are blocked, a relaxation in smooth muscle tissue results.[14] This mechanism decreases resistance to urinary flow, reduces discomfort associated with BPH, and facilitates passage of kidney stones.[14]

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. The U.S. patent expired in October 2009.[25] The U.S. Food and Drug Administration (FDA) approved generics in March 2010.[26] In 2010, tamsulosin was available as OTC medication in UK.[27]

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 Urimax 0.4(India), Flomax, Flomaxtra, Contiflo XL, bestflo, Mecir LP (France), Urimax and Pradif,[28] although generic, non-modified-release capsules are still approved and marketed in many countries (such as Canada). Generic extended-release tablets are marketed in most countries of the EEA.[29] 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.[30] In Egypt,[31] Italy, Russia 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). Tamsulosin hydrochloride is marketed in Bangladesh under the trade names Uromax, Prostanil MR, Tamisol MR, Tamsin.[citation needed]

Society and culture


In the United Kingdom, it costs the NHS 0.04 pounds per dose as of 2018.[5] In 2017, it was the 35th most commonly prescribed medication in the United States, with more than 20 million prescriptions.[9][10]


  1. "Tamsulosin". Merriam-Webster Dictionary.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 "Tamsulosin Hydrochloride Monograph for Professionals". Drugs.com. AHFS. Retrieved 24 December 2018.
  3. 3.0 3.1 "Prostatitis". NHS. 19 October 2017. Retrieved 24 December 2018.
  4. 4.0 4.1 4.2 4.3 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. 69 (3): 353–361.e3. doi:10.1016/j.annemergmed.2016.06.044. PMID 27616037.
  5. 5.0 5.1 5.2 5.3 5.4 5.5 British national formulary : BNF 76 (76 ed.). Pharmaceutical Press. 2018. p. 767. ISBN 9780857113382.
  6. 6.0 6.1 "WHOCC - ATC/DDD Index". www.whocc.no. Retrieved 9 September 2020.
  7. Hutchison, Lisa C.; Sleeper, Rebecca B. (2010). Fundamentals of Geriatric Pharmacotherapy: An Evidence-Based Approach. ASHP. p. 209. ISBN 9781585283057.
  8. "NADAC as of 2018-12-19". Centers for Medicare and Medicaid Services. Retrieved 22 December 2018.
  9. 9.0 9.1 "The Top 300 of 2020". ClinCalc. Retrieved 11 April 2020.
  10. 10.0 10.1 "Tamsulosin Hydrochloride - Drug Usage Statistics". ClinCalc. 23 December 2019. Retrieved 11 April 2020.
  11. "Tamsulosin Aids Stone Expulsion". Renal and Urology News. 7 January 2011.
  12. "Study Shows Use of Tamsulosin or Nifedipine Helps Patients to Clear Ureteral Stone Fragments Faster and Reduces Rate of Recurrence".
  13. 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.
  14. 14.0 14.1 14.2 Lewis, Sharon Mantik. Medical-surgical nursing : assessment and management of clinical problems. Dirksen, Shannon Ruff,, Heitkemper, Margaret M. (Margaret McLean),, Bucher, Linda,, Harding, Mariann (Ninth ed.). St. Louis, Missouri. ISBN 978-0-323-10089-2. OCLC 228373703.
  15. 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.
  16. FDA approval letter at FDA.gov
  17. Australian Medicines Handbook[full citation needed]
  18. "Tamsulosin (Oral Route) - Before Using". Mayo Clinic. Retrieved 5 June 2015.
  19. Medscape, Good Cataract Surgery Outcomes Possible in Intraoperative Floppy Iris Syndrome Due to Tamsulosin.
  20. 20.0 20.1 Bird, ST; Delaney, JA; Brophy, JM; Etminan, M; Skeldon, SC; Hartzema, AG (5 November 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. PMC 3817852. PMID 24192967.
  21. Ramirez, J (5 November 2013). "Severe hypotension associated with α blocker tamsulosin". BMJ (Clinical Research Ed.). 347: f6492. doi:10.1136/bmj.f6492. hdl:10906/78488. PMID 24192968.
  22. Page RL, 2nd; O'Bryant, CL; Cheng, D; Dow, TJ; Ky, B; Stein, CM; Spencer, AP; Trupp, RJ; Lindenfeld, J; American Heart Association Clinical Pharmacology and Heart Failure and Transplantation Committees of the Council on Clinical Cardiology; Council on Cardiovascular Surgery and Anesthesia; Council on Cardiovascular and Stroke Nursing; and Council on Quality of Care and Outcomes, Research. (9 August 2016). "Drugs That May Cause or Exacerbate Heart Failure: A Scientific Statement From the American Heart Association". Circulation. 134 (6): e32–69. doi:10.1161/CIR.0000000000000426. PMID 27400984.CS1 maint: multiple names: authors list (link)
  23. "Tamsulosin Side Effects". Drugs.com. Retrieved 27 April 2011.
  24. Shen, Howard (2008). Illustrated Pharmacology Memory Cards: PharMnemonics. Minireview. p. 13. ISBN 978-1-59541-101-3.
  25. "Flomax – Big Patent Expirations of 2010". 10 February 2010. Retrieved 14 January 2012.
  26. "FDA Approves First Generic Tamsulosin to Treat Enlarged Prostate Gland" (Press release). U.S. Food and Drug Administration (FDA). 2 March 2010.
  27. "OTC tamsulosin for benign prostatic hyperplasia". Drug and Therapeutics Bulletin. 48 (10): 113–6. October 2010. doi:10.1136/dtb.2010.10.0052. PMID 20926447.
  28. Dr. Sandro Magnanelli; Dr.ssa Ada Maria Vetere. "Pradif 0,4 Mg Capsule Rigide A Rilascio Prolungato". Torrinomedica.it. Retrieved 15 November 2012.
  29. Mylan. "Tamsulosina Mylan 0,4 mg cápsulas duras de liberación modificada EFG" (PDF). cima.aemps.es. Retrieved 29 October 2018.
  30. "Drugs.com Database".
  31. "Novartis hits Astellas with transplant drug generic". Reuters. 11 August 2009. Retrieved 11 August 2009.

External links

  • "Tamsulosin". Drug Information Portal. U.S. National Library of Medicine.