|Trade names||omnic, Flomax|
|Bioavailability||100% (by mouth)|
|Elimination half-life||9–13 hours|
|Chemical and physical data|
|3D model (JSmol)|
Tamsulosin, sold under the trade name Alna ® / Flomax ®, is a medication used to treat symptomatic benign prostatic hyperplasia (BPH) and chronic prostatitis, help with the passage of kidney stones, 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 making it easier to urinate. 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. The U.S. Food and Drug Administration (FDA) approved generics in March 2010.
Tamsulosin is primarily used for benign prostatic hyperplasia and to help with the passage of kidney stones. Tamsulosin, however, appears to be effective only for stones over 4 mm and less than 10 mm in size.
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.
- Immunologic: Higher risk of allergic reaction in those with sulfa allergies.
- 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.
- Severe hypotension.
- Persons with cardiac conditions including hypotension, mechanical heart failure (valvular, pulmonary embolism, pericarditis) and congestive heart failure should be monitored carefully while taking tamsulosin.
- In a retrospective analysis of 388 patients with HF (heart failure) and benign prostatic hypertrophy receiving alpha blockers, including prazosin, terazosin, doxazosin, or tamsulosin, Dhaliwal and colleagues found no significant increase in all-cause mortality and HF re-hospitalization in those also receiving β-blockers. However, in those not receiving β-blockade, α-blockade exposure was associated with an increase in HF hospitalization (HR, 1.94; 95% CI, 1.14–3.32). Of note, the majority of patients were receiving tamsulosin (58%). It has been hypothesized that unopposed α1 blockade could lead to β1-receptor stimulation with increases in renin and aldosterone, leading to edema and weight gain. Chronic α1 antagonism may lead to tachyphylaxis according to the American Heart Association ( Drugs That May Cause or Exacerbate Heart Failure, A Scientific Statement From the American Heart Association, Urological Medications). Additionally, several reasons have been proposed for an increased risk of HF in patients receiving alpha blockers such as doxazosin as noted by the American Heart Association; these reasons include misdiagnosis of vasodilator-induced edema, a smaller blood pressure reduction with doxazosin, and the unmasking of HF by the discontinuation of other antihypertensive drugs that were protective against HF.
- 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.
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. The CombAT trial became the medication Jalyn. It was approved by the FDA on 14 June 2010. 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.
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.
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 Urimax 0.4(India), Flomax, Flomaxtra, Contiflo XL, bestflo, Urimax and Pradif, 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. In Egypt, 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, Tamisol MR, Tamsin.
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- Approval letter
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