Dutasteride: Another Inhibitor of DHT

In 2002, the FDA approved a drug called Avodart (dutasteride 0.5 mg) for the treatment of prostate enlargement in men, but the drug also works to inhibit DHT and therefore permit hair growth. This article helps you understand dutasteride and how it may be able to treat your hair loss.

Dutasteride isn't approved specifically for the treatment of male pattern hair loss, and there are no long-term studies assessing its safety and efficacy in hair loss, although short-term study results have been promising.

How dutasteride works

Like finasteride, dutasteride inhibits the enzyme 5AR, which is responsible for the conversion of testosterone to DHT. However, unlike finasteride, which only inhibits one type of the enzyme, dutasteride inhibits both types, making the drug possibly more potent but also increasing the incidence of adverse reactions and side effects.

A dosage of dutasteride 0.5 mg per day decreases serum DHT 91 percent and scalp DHT 54 percent. In comparison, 5 mg finasteride decreases serum DHT 71 percent and scalp DHT 38 percent. Based on these numbers, you may expect dutasteride to be more effective in the treatment of male pattern hair loss than finasteride.

However, because the type of 5AR that dutasteride blocks isn't present in significant quantities in the hair follicle, the effects may not significant. Further studies are needed to answer this important question of which is more effective: dutasteride or finasteride.

Assessing the efficacy of dutasteride

Only a couple of studies have examined the effectiveness of dutasteride for pattern hair loss.

In 2007, a study was published that compared the efficacy of dutasteride to that of placebo in the treatment of androgenetic alopecia in 17 pairs of identical twin males over a one-year period. One twin from each pair received dutasteride 0.5 mg/day for 12 months while the other received placebo.

At the end of the study 15 of the 17 sets of twins correctly guessed which one was using dutasteride. The investigators concluded that dutasteride significantly improves hair growth and reduces hair loss progression in men with male pattern hair loss.

In 2006, a larger study was conducted with 416 men. The participants received either dutasteride (in doses of 0.05, 0.1, 0.5 or 2.5 mg), finasteride 5 mg, or placebo daily for 24 weeks. The investigators found that dutasteride increased area hair count versus placebo, with the level of success depending on the dosage.

In addition, dutasteride 2.5 mg was superior to finasteride 5 mg at 12 and 24 weeks. Scalp and serum dihydrotestosterone levels decreased, and testosterone levels increased, both with the level of success depending on the dosage. A major limitation of this study was that it was limited to only 24 weeks.

What are dutasteride's side effects?

Dutasteride has a greater incidence of sexual side effects compared to finasteride. Dutasteride was investigated in controlled multicenter studies involving men aged 50 and above with prostate enlargement. Drug-related side effects during the first six months included impotence (at 4.7 percent, the highest percentage of occurrence), decreased libido, ejaculation disorders, and breast tenderness and breast enlargement (at 0.5 percent, the lowest percentage of occurrence).

The good news is that most drug-related sexual side effects decreased with time in this study. However, drug-related breast tenderness and breast enlargement remained constant over the treatment period.

In recent cases, dutasteride has caused significant drops in sperm count, which could result in problems with male fertility. As with finasteride, dutasteride reduces the amount of PSA measured in the blood, which must be taken into account when PSA levels are used in the detection of prostate cancer. Women who are pregnant or may become pregnant shouldn't handle dutasteride because of the possibility of absorbing it through the skin and subsequent potential risk to a male fetus.

Dutesteride hangs around in your bloodstream much longer that finasteride does; the half-life of dutasteride is five weeks compared to six to eight hours for finasteride, and blood tests can detect dutasteride in your system up to four to six months after you stop taking the drug. Therefore, you shouldn't donate blood until at least six months after you final dose of dutasteride to prevent giving it to a pregnant woman through a blood transfusion.

At the time of this writing, dutasteride is being researched in an approved FDA format. This study is expected to address all the issues concerning safety and effectiveness of dutasteride as well as the side effects. Stay tuned and talk to your doctor.