Classic studies from the Past: A Look at the Early Dutasteride Studies

Dutasteride vs Finasteride: Suppression of DHT

In the world of hair loss, we often quote numbers and statistics. We frequently throw around information without a good idea of where that information actually came from. An important study is a 2004 study by Dr. Clark and colleagues. It is one of the the classic studies examining how DHT changes with use of finasteride and dutasateride. 

The researchers studied 399 men with prostate enlargement (BPH) and randomized them to once-daily dosing for dutasteride (0.01, 0.05, 0.5, 2.5, or 5.0 mg), or 5 mg finasteride, or placebo for a total of 24 weeks. The percent decrease in DHT was 98% with 5.0 mg dutasteride and 95% with 0.5 mg dutasteride. This was found to be significantly lower than the 71% suppression observed with 5 mg finasteride.  Moreover there was less variability in DHT changes with dutasteride than finasteride. 

Clark et al. Marked suppression of dihydrotestosterone in men with benign prostatic hyperplasia by dutasteride, a dual 5alpha-reductase inhibitor. J Clin Endocrinol Metab. 2004

The other important part of their studies was the increased in DHT that follows stopping the medication. The graph above shows that DHT levels rise much more slowly when dutasteride is stopped than when finasteride is stopped. This is on account of the long half life of dutasteride compared to finasteride (6 hours for finasteride and 4-5 weeks for dutasteride).

Reference

Clark RV, et al. Marked suppression of dihydrotestosterone in men with benign prostatic hyperplasia by dutasteride, a dual 5alpha-reductase inhibitor. Randomized controlled trial. J Clin Endocrinol Metab. 2004.