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Propecia (Finasteride)
- Generic name: Finasteride
- Brand names: Propecia, Proscar
- Dosages: Tablets 1 mg, 5 mg
- Pharmacologic category: 5-alpha-reductase inhibitor
- FDA approved: December 19, 1997
- Pregnancy risk factor: X
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Medical uses
Propecia (Finasteride) is a specific type II 5-alpha reductase
inhibitor. It inhibits the enzyme responsible for regulating conversion
of testosterone to dihydrotestosterone (DHT). By reducing DHT
levels in the scalp, finasteride decreases DHT effects on the hair
follicles, reversing the process of hair loss.
Finasteride indicated uses include:
- Male pattern hair loss (androgenic alopecia) in men only
- Benign prostatic hyperplasia (BPH) in men with enlarged prostate
Propecia works for mild to moderate male pattern hair loss on the vertex (top of head) and anterior mid-scalp
area (middle front of head). There is not sufficient evidence that it works for receding hairlines at the temples.
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Results for hair growth
According to the 5-year clinical study2 9 of 10 men who take Propecia
have visible results - either regrowth of hair (48%) or no further hair loss (42%). Two of 3 men can expect to
regrow hair. A majority of men who took Propecia reported that their bald spot got smaller, their hair loss
slowed down, and the appearance of their hair improved.
Taking finasteride for over 5 years can decrease the likelihood of developing further visible hair
loss by 93%4.
When to expect results?
Daily use for three months or more may be necessary until a person will notice increased hair growth. It can
take 12 months to see the full benefit and to judge how well it’s working for you.
You will need to take Propecia for as long as you want to grow or maintain your hair.
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Pharmacological characteristics
- Absorption: bioavailability is 65%.
- Metabolism: Extensively metabolized in the liver, primarily
via the CYP-450 3A4 enzyme subfamily. Propecia has two active
metabolites: t-butyl side chain monohydroxylated and monocarboxylic
acid. Each metabolite possesses no more than 20% activity.
- Elimination half-life: 3.3 to 13.4 h
- Excretion: 32% to 46% is excreted in the urine as metabolites,
and 51% to 64% is excreted in the feces.
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Benefits
- Increases growth and reduces hair loss
- No drug interactions of clinical importance
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Concerns
- Improvement takes 6-12 months.
- Does not cure androgenic alopecia. Once you stop taking Propecia, you will likely lose any hair you
have gained within 12 months.
- Increased risk of sexual disturbances. The most common side effects are decreased libido,
impotence, decreased volume of ejaculate.
- Expensive
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Unlabeled uses
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Mode of action
Male pattern hair loss, or androgenetic alopecia, is an androgen-dependent balding. In genetically
susceptible men, dihydrotestosterone (DHT), a potent metabolite of the male androgen testosterone,
contributes to miniaturization of hair follicles and a shortened hair growth cycle. The conversion of testosterone
to DHT is regulated by the enzyme 5-alpha reductase, which is found primarily in scalp follicles.
Finasteride is a competitive and specific inhibitor of Type II 5-alpha-reductase, an intracellular enzyme
that converts the androgen testosterone into 5α-dihydrotestosterone. The type II 5-alpha-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.
Finasteride decreases DHT concentrations in the serum and the scalp by up
to 70 and 60%, respectively. This prevents the miniaturisation of the scalp hair follicles, leading to reversal
of the balding process. Finasteride may affect hair growth through reductions in scalp and serum DHT because the
scalp is highly vascularized.
Finasteride has no affinity for the androgen receptor and has no androgenic, antiandrogenic,
estrogenic, antiestrogenic, or progestational effects. |
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Reviews, Discussion Boards & Forums
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References
- Propecia official site
- Finasteride on DermNet.NZ
- 1. U.S. FDA Propecia
Prescribing Information
- 2. Long-term (5-year) multinational experience with finasteride 1 mg in the treatment of
men with androgenetic alopecia. Eur J Dermatol. 2002 Jan-Feb;12(1):38-49.
- 3. Beigi A, Sobhi A, Zarrinkoub F. Finasteride versus cyproterone acetate-estrogen
regimens in the treatment of hirsutism. Int J Gynaecol Obstet. 2004 Oct;87(1):29-33.
PubMed
- 4. Kaufman KD, Rotonda J, Shah AK, Meehan AG. Long-term finasteride
treatment decreases the likelihood of developing further visible hair loss in men with androgenetic alopecia.
Eur J Dermatol. 2008 Jul-Aug;18(4):400-6
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Interesting facts
- Men with a genetic deficiency of 5α-reductase do not suffer from androgenic alopecia.
- At the end of 2004 the World Anti-Doping Agency (WADA) added finasteride to its Prohibited list.
It is known to be a "masking agent" for a number of performance-enhancing steroids banned by WADA.
- Propecia was initially approved by the FDA as a prostate gland shrinking prescription.
- However in 1998 it was also approved at a lower dosage as an anti-baldness treatment.
- It is sold as a prescription prostate medication in 5 mg tablet
form under the brand name Proscar and for treatment
of baldness it is sold in 1 mg tablets under the brand name Propecia.
- It is the first and the only FDA-approved oral treatment for male androgenetic alopecia on the vertex
and the anterior mid-scalp.
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