Dutasteride, a dual 5-alpha-reductase inhibitor, was approved by the FDA for the treatment of BPH and should be in the pharmacies sometime in March. It can be used interchangeably with Propecia/Poscar in our recommended protocol.
2001 U.S. FDA Drug Approval
Approved November 20, 2001
Dutasteride is a specific inhibitor of type 1 and 2 isoforms of 5-alpha reductase; it inhibits the conversion of testosterone to dihydrotestosterone.
The usual dose of dutasteride is 0.5 milligram (mg) (one capsule) orally once a day, with or without food.
Peak plasma dutasteride concentrations occur 2 to 3 hours after oral administration. Oral bioavailability is approximately 60%. The volume of distribution ranges from 300 to 500 liters (L). Protein binding is extensive, approximately 99% to albumin and 96.6% to alpha-1 acid glycoprotein. The half-life is approximately 5 weeks. Dutasteride is extensively metabolized, mainly by the cytochrome P450 CYP3A4 isoenzyme, and not by CYP1A2, CYP2C9, CYP2C19, or CYP2D6. The drug is excreted mainly in the feces, approximately 5% unchanged and 40% as metabolites. Trace amounts (less than 1%) are excreted in the urine, leaving 55% of an administered dose unaccounted for.
Sexual dysfunction is the primary adverse event with dutasteride therapy including impotence, decreased libido and ejaculatory disturbances. Gynecomastia has also been reported. Dutasteride is CONTRAINDICATED in pregnancy (FDA Pregnancy Category X). It is absorbed through the skin, and should not be handled by pregnant women.
Dutasteride is indicated for the treatment of symptomatic benign prostatic hyperplasia in patients 18 years of age or older. It is under investigation for the treatment of adult male pattern hair loss (androgenetic alopecia). The side effects will likely be more pronounced with Dutasteride compared with Propecia/Proscar, necessitating the need for an aromatase inhibitor (such as Arimidex or Super Miraforte) in many users. Data thus far show it to be better than Propecia/Proscar at growing hair.