Glossary

Dutasteride

A 5α-reductase inhibitor that blocks both type 1 and type 2 enzymes, lowering scalp DHT by approximately 90%. FDA-approved for BPH; off-label for male AGA in most countries (approved for AGA in South Korea and Japan).

Also: Avodart

Dutasteride is a dual inhibitor of type 1 and type 2 5α-reductase. It produces deeper DHT suppression than finasteride: approximately 90% scalp DHT reduction and approximately 98% serum DHT reduction at the standard 0.5 mg/day dose, compared with finasteride’s 64 to 70% scalp and 70% serum.

The deeper DHT suppression translates into modestly better hair counts than finasteride in head-to-head trials. Side-effect profiles are broadly similar.

Regulatory status:

FDA-approved for BPH (benign prostatic hyperplasia) in the US, EU, and most countries.
FDA-approved for AGA specifically in South Korea and Japan.
Off-label for AGA in the US, UK, EU, and most other countries.

Half-life is much longer than finasteride (roughly 5 weeks vs 6 hours), so the drug accumulates over the first few months and clears slowly after stopping. This matters for fertility planning and surgical contexts.

Often used in men who plateau on finasteride or want maximum DHT suppression. Standard combination with topical minoxidil applies. Same precautions in pregnancy as finasteride: not for women of reproductive age.