Drug Breakdown: FINASTERIDE

Abstract
In this column, Sharon Rees aims to refresh knowledge and interest in some of the commonly used drugs in a series of posts on X. This month she is talking about #finasteride
Day 1: #finasteride is a synthetic steroid derivative. In the 1940s & 70s links with prostate/testicular conditions & hair loss were reported. This led to the discovery of 5-alpha reductase enzyme. #finasteride was the 1st drug inhibitor of this enzyme. Licensed in the 1990s for benign prostatic hyperplasia (BPH) & male pattern hair loss.
Day 2: #finasteride is orally active. Regimens are 5mg x1/day for BPH & 1mg/day for hair loss. The drug needs to be taken continuously (both indications) for several months for benefit. Licensed adult men; 5-alpha reductase inhibitors are contra-indicated in women because of potential harm to a male fetus. Currently no licensed topical formulation for #finasteride or dutasteride for androgenic alopecia. Topical finasteride is available on private prescription/online in UK as unlicensed product
Day 3: Kinetics #finasteride. Good oral absorption & bioavailability & high Vd. Hepatic metabolism via CYP3A4 > mildly active metabolites. Excretion 60:40 faeces:urine. T½ 6hrs, but re hair loss treatment, it takes weeks>months to impact hormone levels sufficient for visible hair changes
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