weeks following treatment with mifepristone. Avoid cyclosporine, dihydroergotamine, ergotamine, fentanyl, pimozide, quinidine, sirolimus, and tacrolimus. Risk D: Consider therapy modification
Peginterferon Alfa-2b: May decrease the serum concentration of CYP2D6 Substrates. Risk C: Monitor therapy
Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Alpha1-Blockers. Management: Ensure patient is stable on one agent prior to initiating the other, and always initiate combination using the lowest possible dose of the drug being added. When tadalafil is used for treatment of BPH, concurrent alpha 1-blockers are not recommended. Risk D: Consider therapy modification
Tocilizumab: May decrease the serum concentration of CYP3A4 Substrates. Risk C: Monitor therapy
Ethanol/Nutrition/Herb Interactions
Food: Fasting increases bioavailability by 30% and peak concentration 40% to 70%. Management: Administer 30 minutes after the same meal each day.
Herb/Nutraceutical: St John’s wort may decrease the levels/effects of tamsulosin. Some herbal medications have hypotensive properties or may increase the hypotensive effect of tamsulosin. Limited information is available regarding combination with saw palmetto. Management: Avoid St John's wort, black cohosh, California poppy, coleus, golden seal, hawthorn, mistletoe, periwinkle, quinine, and shepherd's purse. Avoid saw palmetto.
Pregnancy Risk Factor
B (show table)
Pregnancy Implications
Teratogenic effects were not observed in animal studies.
Dietary Considerations
Take once daily, 30 minutes after the same meal each day.
Pricing: U.S. (
www.drugstore.com)
Capsules (Flomax)
0.4 mg (30): $153.99
Capsules (Tamsulosin HCl)
0.4 mg (30): $122.99
International Brand Names
• Alna (AT, DE);
• Comadex (EC);
• Flomax (NZ, TR);
• Flomaxtra (AU, NZ);
• Flomaxtra XL (GB);
• Harnal (CL, HK, JP, PH, TH);
• Harnal D (ID);
• Harnal OCAS (ID, MY, PH, SG);
• Harnalidge D (TW);
• Harusin SR (KP);
• Josir (FR);
• Lutsnal (KP);
• Mecir LP (FR);
• Omexel LP (FR);
• Omic (BE, LU);
• Omix Ocas (CH);
• Omnexel (IE);
• Omnic (AR, CN, CO, CZ, DE, DK, EE, ES, FI, GR, HU, IL, IT, NL, NO, PE, PL, PT, PY, RU);
• Omnic OCAS (IL);
• Omnic Tocas (BG);
• Pimax (PH);
• Pradif (PT);
• Promnix (IL);
• Prozelax (PH);
• Secotex (AR, CN, CO, CR, DO, GT, HN, MX, NI, PA, PE, PY, SV, UY, VE);
• Secotex OCAS (CR, DO, EC, GT, HN, NI, PA, SV);
• Sulosin (KP);
• Sulosin D (KP);
• Tabphyn MR (GB);
• Tamlosin (TW);
• Tamlosin SR (KP);
• Tamsulin (IL);
• Tamsulo (KP);
• Tamsulon (CR, DO, EC, GT, HN, NI, SV);
• Tamunal (KP);
• Tarunal (KP);
• Urimax (IN);
• Urnal (TW);
• Urotams SR (KP);
• Zotan (TW)
Mechanism of Action
Tamsulosin is an antagonist of alpha1A-adrenoreceptors in the prostate. Smooth muscle tone in the prostate is mediated by alpha1A-adrenoreceptors; blocking them leads to relaxation of smooth muscle in the bladder neck and prostate causing an improvement of urine flow and decreased symptoms of BPH. Approximately 75% of the alpha1-receptors in the prostate are of the alpha1A subtype.
Pharmacodynamics/Kinetics
Absorption: >90%
Distribution: Vd: 16 L
Protein binding: 94% to 99%, primarily to alpha1 acid glycoprotein (AAG)
Metabolism: Hepatic (extensive) via CYP3A4 and 2D6; metabolites undergo extensive conjugation to glucuronide or sulfate
Bioavailability: Fasting: 30% increase
Steady-state: By the fifth day of once-daily dosing
Half-life elimination: Healthy volunteers: 9-13 hours; Target population: 14-15 hours
Time to peak: Fasting: 4-5 hours; With food: 6-7 hours
Excretion: Urine (76%, <10% as unchanged drug); feces (21%)
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REFERENCES
1. Agrawal M, Gupta M, Gupta A, et al, “Prospective Randomized Trial Comparing Efficacy of Alfuzosin and Tamsulosin in Management of Lower Ureteral Stones,” Urology, 2009, 73(4):706-9. [PubMed 19193417]
2. Ahmed AF and Al-Sayed AY, “Tamsulosin versus Alfuzosin in the Treatment of Patients with Distal Ureteral Stones: Prospective, Randomized, Comparative Study,” Korean J Urol, 2010, 51(3):193-7. [PubMed 20414396]
3. Chang DF and Campbell JR, “Intraoperative Floppy Iris Syndrome Associated With Tamsulosin,” J Cataract Refract Surg, 2005, 31(4):664-73. [PubMed 15899440]
4. Goldman HB and Zimmern PE, “The Treatment of Female Bladder Outlet Obstruction,” BJU Int, 2006, 98(Suppl 1):17-23. [PubMed 16911596]
5. Pischedda A, Pirozzi Farina F, Madonia M, et al, “Use of Alpha1-Blockers in Female Functional Bladder Neck Obstruction,” Urol Int, 2005, 74(3):256-61. [PubMed 15812214]
6. Rossi C, Kortmann BB, Sonke GS, et al, “Alpha-Blockade Improves Symptoms Suggestive of Bladder Outlet Obstruction But Fails to Relieve It,” J Urol, 2001, 165(1):38-41. [PubMed 11125359]