Dutasteride

Dutasteride is a synthetic oral medication that belongs to the class of 5-alpha-reductase inhibitors. It inhibits the conversion of testosterone to dihydrotestosterone (DHT) by blocking both type I and type II isoenzymes, reducing DHT levels systemically. It is approved for benign prostatic hyperplasia (BPH) and is marketed under brand names such as Avodart. In some regions it is used off-label for androgenetic alopecia.

In BPH, lowered DHT results in slowed progression and often a reduction in prostate size, which can improve urinary symptoms and flow. In hair loss, the rationale is decreased scalp DHT production, but efficacy varies and regulatory approval differs by country.

Dutasteride is taken as a 0.5 mg oral capsule once daily for BPH, with a combination product containing tamsulosin approved as Jalyn. It has a long elimination half-life of several weeks, and is mainly metabolized by CYP3A4. It is not rapidly eliminated; steady-state levels accumulate with continued dosing.

Adverse effects are primarily sexual, including reduced libido, erectile dysfunction, and ejaculation disorders; breast tenderness or enlargement can occur. Rare hypersensitivity reactions and other effects may occur. There is concern about an increased relative risk of high-grade prostate cancer with 5-alpha-reductase inhibitors; monitoring of PSA is necessary, and dutasteride lowers PSA levels by about 50%, so values must be adjusted when assessing prostate cancer risk. Pregnant women should avoid handling intact tablets; exposure to the medication should be avoided during pregnancy due to risk to male fetuses.

Dutasteride should be used under medical supervision, with consideration of contraindications, drug interactions (notably CYP3A4 inhibitors or inducers), and monitoring for side effects and PSA changes.