Comparison of finasteride (Proscar), a 5 alpha reductase inhibitor, and various commercial plant extracts in in vitro and in vivo 5 alpha reductase inhibition.
Human prostate was used as a source of 5 alpha reductase. Compounds were incubated with an enzyme preparation and [3H]testosterone. [3H]-dihydrotestosterone production was measured to calculate 5 alpha reductase activity. IC50 values (ng/ml) were finasteride = 1; Permixon = 5,600; Talso = 7,000; Strogen Forte = 31,000; Prostagutt = 40,000; and Tadenan = 63,000. Bazoton and Harzol had no activity at concentrations up to 500,000 ng/ml. In castrate rats stimulated with testosterone (T) or dihydrotestosterone (DHT), finasteride, but not Permixon or Bazoton, inhibited T stimulated prostate growth, while none of the three compounds inhibited DHT stimulated growth. These results demonstrate that finasteride inhibits 5 alpha reductase, while Permixon and Bazoton have neither anti-androgen nor 5 alpha reductase inhibitory activity. In addition, in a 7 day human clinical trial, finasteride, but not Permixon or placebo, decreased serum DHT in men, further confirming the lack of 5 alpha reductase inhibition by Permixon. Finasteride and the plant extracts listed above do not inhibit the binding of DHT to the rat prostatic androgen receptor (concentrations to 100 micrograms/ml). Based on these results, it is unlikely that these plant extracts would shrink the prostate by inhibiting androgen action or 5 alpha reductase.
Department of Biochemistry, Merck Research Laboratories, Rahway, New Jersey 07065.
L
L
Rhodes
R L
RL
Primka
C
C
Berman
G
G
Vergult
M
M
Gabriel
M
M
Pierre-Malice
B
B
Gibelin
D058891:5-alpha Reductase Inhibitors; D000736:Androstenes / Q000494:pharmacology*; D000818:Animals; D001378:Azasteroids / Q000494:pharmacology*; D013196:Dihydrotestosterone / Q000097:blood; D018120:Finasteride; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D010936:Plant Extracts / Q000494:pharmacology*; D011467:Prostate / Q000187:drug effects / Q000201:enzymology; D051381:Rats; D011944:Receptors, Androgen / Q000187:drug effects; D028024:Serenoa; D013739:Testosterone / Q000097:blood
D058891:5-alpha Reductase Inhibitors; D000736:Androstenes; D001378:Azasteroids; D010936:Plant Extracts; D011944:Receptors, Androgen; D013196:Dihydrotestosterone; D013739:Testosterone; D018120:Finasteride; C040972:saw palmetto extract