| Item |
Information |
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Drug Groups
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approved |
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Description
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An orally active testosterone 5-alpha-reductase inhibitor. It is used as a surgical alternative for treatment of benign prostatic hyperplasia. [PubChem] |
| Indication |
For the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate to: Improve symptoms, reduce the risk of acute urinary retention, reduce the risk of the need for surgery including transurethral resection of the prostate. Also used for the stimulation of regrowth of hair in men with mild to moderate androgenetic alopecia (male pattern alopecia, hereditary alopecia, common male baldness). |
| Pharmacology |
Finasteride is a synthetic 4-azasteroid compound. This drug is a competitive and specific inhibitor of Type II 5a-reductase, an intracellular enzyme that converts the androgen testosterone into 5α-dihydrotestosterone (DHT). Two distinct isozymes are found in mice, rats, monkeys, and humans: Type I and II. Each of these isozymes is differentially expressed in tissues and developmental stages. In humans, Type I 5a-reductase is predominant in the sebaceous glands of most regions of skin, including scalp, and liver. Type I 5a-reductase is responsible for approximately one-third of circulating DHT. The Type II 5a-reductase isozyme is primarily found in prostate, seminal vesicles, epididymides, and hair follicles as well as liver, and is responsible for two-thirds of circulating DHT. Although finasteride is 100-fold more selective for type II 5a-reductase than for the type I isoenzyme, chronic treatment with this drug may have some effect on type I 5a-reductase. |
| Affected Organisms |
| • |
Humans and other mammals |
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| Biotransformation |
Drug is extensively metabolized, primarily in the liver via CYP3A4. Two metabolites have been identified with ≤20% of the activity of finasteride. |
| Half Life |
4.5 hours (range 3.3-13.4 hours) |
| Protein Binding |
Approximately 90% |
| Elimination |
Following an oral dose of 14C-finasteride in man (n = 6), a mean of 39% (range, 32 to 46%) of the dose was excreted in the urine in the form of metabolites; 57% (range, 51 to 64%) was excreted in the feces. Urinary excretion of metabolites was decreased in patients with renal impairment. This decrease was associated with an increase in fecal excretion of metabolites. |
| Distribution |
* 44 to 96 L |
| Clearance |
* 165 mL/min [healthy young subjects] |
| References |
| • |
Suzuki R, Satoh H, Ohtani H, Hori S, Sawada Y: Saturable binding of finasteride to steroid 5alpha-reductase as determinant of nonlinear pharmacokinetics. Drug Metab Pharmacokinet. 2010;25(2):208-13.
[Pubmed]
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| • |
Smith AB, Carson CC: Finasteride in the treatment of patients with benign prostatic hyperplasia: a review. Ther Clin Risk Manag. 2009 Jun;5(3):535-45. Epub 2009 Jul 12.
[Pubmed]
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| External Links |
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