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tamsulosin (Flomax, Urolosin)

Tradename: Flomax. FDA-approved generic March 3, 2010 Indications: 1) benign prostatic hypertrophy 2) easing passage of urinary calculus [6] Contraindications: -> concurrent use of other alpha-adrenergic antagonists Dosage: start 0.4 mg PO QHS; maximum 0.8 mg QHS Capsules: 0.4 mg, 0.8 mg (Do Not crush) {NOT suitable for G-tube} No dosage adjustment with renal insufficiency. Pharmacokinetics: 1) > 90% absorption of oral dose (fasting) 2) maximum serum concentration reached 4-5 hours after oral dose (fasting) 3) food somewhat impairs & delays absorption (30%) 4) 90-94% bound to serum protein, primarily alpha-1 acid glycoprotein 5) extensively metabolized by cytochrome P450 a) metabolites conjugated prior to elimination in the urine (76%) b) 21% eliminated in the feces 6) < 10% excreted unchanged in the urine 7) linear elimination kinetics 8) t1/2 9-15 hours 9) steady-state concentrations reached after 5th day of QD dosing 10) maximal response for BPH in 1-2 weeks - clinical improvement may be seen in 8 hours Adverse effects: 1) orthostatic hypotension* (0.2-0.4%) a) 2 fold risk of severe hypotension b) risk especially high early in treatment [10] - up to 8 weeks into treatment c) restarting tamsulosin also associated with risk of severe hypotension [10] 2) somnolence 3) insomnia 4) rhinitis 5) retrograde ejaculation# 6) dizziness 7) cough 8) sinusitis 9) asthenia 10) back pain 11) chest pain 12) amblyopia 13) Intraoperative Floppy Iris Syndrome (IFIS) during phacoemulsification cataract surgery [7,8] - do not initiate tamsulosin therapy prior to scheduled cataract surgery [11] * least likely to cause orthostatic hypotension among alpha-1 blockers [5] # most common among alpha-1 blockers used for BPH Drug interactions: 1) other alpha-adrenergic receptor antagonists 2) cimetidine diminishes clearance of tamsulosin 3) studies of interaction with warfarin are inconclusive Test interaction: 1) none known 2) no effect on PSA Mechanism of action: 1) alpha-1A adrenergic receptor antagonist [3] - 70% of alpha-1 receptors in the prostate are alpha-1A receptors 2) relaxation of smooth muscle in the neck of the bladder & prostate 3) NOT an anti-hypertensive agent [3]

Interactions

drug interactions drug adverse effects (more general classes)

Related

benign prostatic hyperplasia (BPH)

General

alpha-1 adrenergic receptor antagonist; prostate-selective alpha blocker

Properties

SIZE: MW = 408 G/M MISC-INFO: elimination route LIVER protein-binding 95% elimination by hemodialysis - 1/2life 9-15 HOURS

Database Correlations

PUBCHEM correlations

References

  1. www.flomax.bph.com
  2. Physician's Desk Reference (PDR) 54th edition, Medical Economics, 2000
  3. Aronson W. in: UCLA Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 12-15, 2001
  4. Geriatric Dosage Handbook, 6th edition, Selma et al eds, Lexi-Comp, Cleveland, 2001
  5. Prescriber's Letter 10(9):53 2003
  6. Prescriber's Letter 11(9): 2004 Use of Nifedipine or Tamsulosin for Kidney Stones Detail-Document#: 200911 (subscription needed) http://www.prescribersletter.com
  7. FDA Medwatch http://www.fda.gov/medwatch/safety/2005/safety05.htm#Flomax
  8. Bell CM et al Association Between Tamsulosin and Serious Ophthalmic Adverse Events in Older Men Following Cataract Surgery JAMA. 2009;301(19):1991-1996. PMID: 19454637 http://jama.ama-assn.org/cgi/content/full/301/19/1991 - Friedman AH Tamsulosin and the Intraoperative Floppy Iris Syndrome JAMA. 2009;301(19):2044-2045. PMID: 19454645 http://jama.ama-assn.org/cgi/content/extract/301/19/2044
  9. FDA NEWS RELEASE: March 2, 2010 FDA Approves First Generic Tamsulosin to Treat Enlarged Prostate Gland http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm202728.htm
  10. Bird ST et al 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 2013;347:f6320 PMID: 24192967 http://www.bmj.com/content/347/bmj.f6320
  11. Geriatric Review Syllabus, 9th edition (GRS9) Medinal-Walpole A, Pacala JT, Porter JF (eds) American Geriatrics Society, 2016

Component-of

dutasteride/tamsulosin