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5a-Reductase InhibitorAka: Finasteride, Proscar, Propecia, Dutasteride, Duagen

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  1. Indications
    1. Benign Prostatic Hyperplasia
    2. Androgenic Alopecia in males (Finasteride)
      1. Adjunct to hair transplantation
  2. Mechanism
    1. Inhibits Testosterone to Dihydrotestosterone conversion
      1. Competitive inhibition of enzyme 5a-reductase
      2. Finasteride inhibits Type II 5a reductase
      3. Dutasteride inhibits both Type I and II 5a reductase
    2. Reduces volume of prostate
    3. Improves urine blood flow
  3. Dosing
    1. Alopecia
      1. Finasteride 1 mg PO qd
    2. Benign Prostatic Hyperplasia
      1. Finasteride 5 mg PO qd ($63 per month)
  4. Advantages: Finasteride
    1. Alopecia
      1. Increases Hair Growth and reduces Hair Loss
      2. Effective on vertex and anterior mid-scalp
      3. Side effects uncommon
    2. Benign Prostatic Hyperplasia
      1. May be more effective in men with large prostate
  5. Disadvantages: Finasteride
    1. Alopecia
      1. Improvements take 6-12 months
      2. Any benefits are lost when medication is stopped
      3. Expensive (Pharmacist's cost: $50/month or $600/year)
    2. Benign Prostatic Hyperplasia
      1. Increased urine flow not evident for 6-12 months
      2. Only mediocre effects on obstructive symptoms and urine flow
        1. Less effective than alpha blockers (e.g. Hytrin)
        2. Less effective than surgery
        3. Only as effective as Saw Palmetto
      3. Highly effective in reducing BPH-related Gross Hematuria (80%)
        1. Kearney (2002) J Urol 167:2489
  6. Adverse Effects
    1. Decreased Libido or Erectile Dysfunction (2%)
    2. Lowers Prostate Specific Antigen (PSA) Values by 30-50%
      1. Obtain PSA baseline prior to starting Finasteride
      2. Double the actual PSA to determine work-up
      3. Obtain baseline Digital Rectal Exam
    3. Longterm use associated with high grade Prostate Cancer
      1. Thompson (2003) N Engl J Med 349:215
  7. References
    1. (1992) Med Lett Drugs Ther 34:83
    2. Nickel (1996) CMAJ 155:1251
    3. Guess (1996) J Urol 155:3

Finasteride (C0060389)

Definition (MSH)An orally active TESTOSTERONE 5-ALPHA-REDUCTASE inhibitor. It is used as a surgical alternative for treatment of benign prostatic hyperplasia.
Definition (CSP)orally active testosterone 5-alpha reductase inhibitor, used as an alternative to surgery for treatment of benign prostatic hyperplasia.
Definition (NCI)A drug used to reduce the amount of male hormone (testosterone) produced by the body.
Definition (PDQ)A synthetic 4-azasteroid compound. Finasteride competitively binds to and inhibits steroid type II 5-alpha-reductase in the prostate gland, liver, and skin, thereby interfering with the enzymatic conversion of testosterone to 5-dihydrotestosterone (DHT) and reducing serum DHT levels. The reduction in serum DHT levels results in diminished stimulation of androgen receptors in the nuclei of prostate cells and, so, diminished prostate cell proliferation. Check for "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=41096&idtype=1" active clinical trials or "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=41096&idtype=1&closed=1" closed clinical trials using this agent. ("http://nciterms.nci.nih.gov:80/NCIBrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&code=C1099" NCI Thesaurus)
Definition (NCI)A synthetic 4-azasteroid compound. Finasteride competitively binds to and inhibits steroid type II 5-alpha-reductase in the prostate gland, liver, and skin, thereby interfering with the enzymatic conversion of testosterone to 5-dihydrotestosterone (DHT) and reducing serum DHT levels. The reduction in serum DHT levels results in diminished stimulation of androgen receptors in the nuclei of prostate cells and, so, diminished prostate cell proliferation.
ConceptsSteroid (T110) , Pharmacologic Substance (T121)
EnglishFinasteride, FINASTERIDE PREPARATION
Spanishfinasterida
CreditsDerived from the NIH UMLS (Unified Medical Language System)


Proscar (C0678149)

ConceptsSteroid (T110) , Pharmacologic Substance (T121)
EnglishCahill May Roberts Brand of Finasteride, Merck Brand 2 of Finasteride, Merck Frosst Brand 2 of Finasteride, Merck Sharp & Dhome Brand 2 of Finasteride, MSD Chibropharm Brand of Finasteride, Proscar
CreditsDerived from the NIH UMLS (Unified Medical Language System)


Propecia (C0722858)

ConceptsSteroid (T110) , Pharmacologic Substance (T121)
EnglishMerck Brand 1 of Finasteride, Merck Frosst Brand 1 of Finasteride, Merck Sharp & Dohme Brand 1 of Finasteride, MSD Brand of Finasteride, Propecia, Propeshia
CreditsDerived from the NIH UMLS (Unified Medical Language System)


Dutasteride (C0754659)

Definition (NCI)A synthetic 4-azasteroid compound. Dutasteride competitively and specifically binds to isoenzymes 1 and 2 of 5 alpha-reductase, forming stable enzyme complexes and inhibiting the conversion of testosterone to 5 alpha-dihydrotestosterone (DHT); the reduction in DHT activity may mitigate or prevent enlargement of the prostate gland. The type 2 5 alpha-reductase isoenzyme is primarily active in the reproductive tissues, while the type 1 isoenzyme is also active in skin and the liver.
Definition (PDQ)A synthetic 4-azasteroid compound. Dutasteride competitively and specifically binds to isoenzymes 1 and 2 of 5-alpha-reductase, forming stable enzyme complexes and inhibiting the conversion of testosterone to 5-alpha-dihydrotestosterone (DHT); the reduction in DHT activity may mitigate or prevent enlargement of the prostate gland. The type 2 5-alpha-reductase isoenzyme is primarily active in the reproductive tissues, while the type 1 isoenzyme is also active in skin and the liver. Check for "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=479183&idtype=1" active clinical trials or "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=479183&idtype=1&closed=1" closed clinical trials using this agent. ("http://nciterms.nci.nih.gov:80/NCIBrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&code=C47503" NCI Thesaurus)
ConceptsOrganic Chemical (T109) , Pharmacologic Substance (T121)
EnglishDutasteride, DUTASTERIDE @ @ UNIDENTIFIED, DUTASTERIDE PREPARATION, DUTASTERIDE UNIDENTIFIED
Spanishdutasterida
CreditsDerived from the NIH UMLS (Unified Medical Language System)



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