Finasteride - Generic Propecia

Finasteride is a competitive and specific inhibitor of Type II 5 alpha-reductase, an intracellular enzyme that converts the androgen testosterone into dihydrotestosterone (DHT). Two distinct isozymes of 5 alpha-reductase 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 5 alpha-reductase is predominant in the sebaceous glands of most regions of skin, including scalp and liver. Type I 5 alpha-reductase is responsible for approximately one-third of circulating DHT. 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.

In humans, the mechanism of action of finasteride is based on its preferential inhibition of the Type II isozyme. Using native tissues (scalp and prostate), in vitro binding studies examining the potential of finasteride to inhibit either isozyme revealed a 100-fold selectivity for the human Type II 5 alpha-reductase over Type I isozyme (IC 50=500 and 4.2 nM for Type I and II, respectively). For both isozymes, the inhibition by finasteride is accompanied by reduction of the inhibitor to dihydrofinasteride and adduct formation with NADP +. The turnover for the enzyme complex is slow (t 1Ä2 approximately 30 days for the Type II enzyme complex and 14 days for the Type I complex).

Finasteride has no affinity for the androgen receptor and has no androgenic, antiandrogenic, estrogenic, antiestrogenic, or progestational effects. Inhibition of Type II 5 alpha-reductase blocks the peripheral conversion of testosterone to DHT, resulting in significant decreases in serum and tissue DHT concentrations. Finasteride produces a rapid reduction in serum DHT concentration, reaching 65% suppression within 24 hours of oral dosing with a 1 mg tablet.

In men with male pattern hair loss (androgenetic alopecia), the balding scalp contains miniaturized hair follicles and increased amounts of DHT compared with hairy scalp. Administration of finasteride decreases scalp and serum DHT concentrations in these men. By this mechanism, finasteride interrupts a key factor in the development of androgenetic alopecia in those patients genetically predisposed.

In a study in 15 healthy male subjects, the mean bioavailability of finasteride 1 mg tablets was 65% (range, 26 to 170%), based on the ratio of AUC relative to a 5 mg i.v. dose infused over 60 minutes. Following the i.v. infusion, mean plasma clearance was 165 mL/min (range, 70 to 279 mL/min) and mean steady-state volume of distribution was 76 L (range, 44 to 96 L). In a separate study, the bioavailability of finasteride was not affected by food.

Approximately 90% of circulating finasteride is bound to plasma proteins. Finasteride has been found to cross the blood-brain barrier.

Due to the drug’s effect on male babies, women should avoid Propecia if there is any chance that they may be pregnant.

Do not use Propecia if it gives you an allergic reaction, or if you’ve ever had an allergic reaction to its chemical twin, Proscar.

Propecia is a pill taken by mouth that is a fairly new and effective treatment for male baldness. An increase in scalp hair count and hair regrowth was seen in over 80% of men for whom it was prescribed. Numerous studies have been done looking at the efficacy of PROPECIA. Overall improvements were seen as quickly as 3 months after starting the medicine. PROPECIA not only led to a decrease in hair loss but also significantly increased the rate of hair regrowth. These effects were maintained for over 2 years with continued PROPECIA therapy.

Propecia should be stored at room temperature between 59 and 86 degrees F (15-30 degrees C) away from light and moisture. Keep this and all medications out of the reach of children.

This drug is taken by mouth. 1 tablet per day. PROPECIA is the brand name for finasteride, which acts to inhibit the conversion of the androgen (male hormone) testosterone into 5-alpha-dihydrotesterone (DHT). In men each hair follicle contains tiny amounts of DHT. As male pattern baldness begins the amount of DHT contained in each follicle increases. PROPECIA through its inhibitory action serves to reverse this process by decreasing the amount of DHT in the hair follicle and in blood.

In clinical studies adverse reactions were noted to be rare and did not affect most men. The most common adverse reaction was decreased libido that appeared to occur in less then 2.0% of men taking this medicine. The problem quickly resolved in all cases upon the discontinuation of the medication.

If you miss a dose, take it as soon as remembered; do not take if it is almost time for the next dose, instead, skip the missed dose and resume your usual dosing schedule. Do not “double-up” the dose to catch up.