A selective inhibitor of 5-alpha reductase (type 1 and 2 isoenzymes) responsible for the conversion of testosterone to 5-alpha dihydrotestosterone. Dihydrotestosterone is the main androgen responsible for the hyperplasia of the glandular tissue of the prostate gland. The maximum decrease in plasma dihydrotestosterone concentrations is dose-dependent and is observed 1–2 weeks after the start of treatment at a dose of 0.5 mg / day (reduced by 85 and 90%, respectively). It reduces the size of the prostate gland, improves urination and reduces the risk of acute urinary retention and the need for surgical treatment.
After a single dose of 500 µg Cmax of dutasteride in serum is reached within 1-3 hours. At 2-hour IV infusion, the absolute bioavailability is about 60%. Bioavailability of dutasteride does not depend on food intake.
Plasma protein binding is high – more than 99.5%. Vd – 300-500 l.
With daily intake, the concentration of dutasteride in serum reaches 65% of Css after 1 month and approximately 90% of this level after 3 months. Css of dutasteride in serum, approximately 40 ng / ml, is achieved after 6 months of the daily intake of the drug at a dose of 500 μg. In semen, as in serum, the Css of dutasteride is also reached after 6 months. After 52 weeks. Treatment of sperm dutasteride concentrations averaged 3.4 ng / ml (0.4-14 ng / ml). Approximately 11.5% of dutasteride comes from sera into semen. Dutahair undergoes intensive metabolism. After the drug is taken orally at a dose of 500 µg / day until an equilibrium state is reached, 1–15.4% (5.4% on average) of the dose taken is excreted in the feces unchanged. The rest of the dose is excreted in the form of 4 major metabolites, accounting for 39%, 21%, 7% and 7%, respectively, and 6 small metabolites (each of which accounts for less than 5%).
Traces of unchanged dutasteride (less than 0.1% of the dose) are excreted in human urine.
When taking Dutahair in therapeutic doses, its final T1 / 2 is 3-5 weeks.
Dutasteride is detected in serum (in concentrations of more than 0.1 ng / ml) up to 4-6 months after discontinuation of its administration.