minutes) is longer than that of testosterone (34 minutes), and this may account for some of the difference in their potency. A study of transdermal androstanolone and testosterone therapy reported terminal half-lives of 2.83 hours and 1.29 hours, respectively. Chemistry Androstanolone, also known as 5α-androstan-17β-ol-3-one or as 5α-dihydrotestosterone (5α-DHT), is a naturally occurring androstane steroid with a ketone group at the C3 position and a hydroxyl group at the C17β position. It is the derivative of testosterone in which the double bond between the C4 and C5 positions has been reduced or hydrogenated. Esters Several C17β ester prodrugs of androstanolone, including androstanolone benzoate, androstanolone enanthate, androstanolone propionate, and androstanolone valerate, have been developed and introduced for medical use as AAS. Conversely, dihydrotestosterone acetate, dihydrotestosterone butyrate, and dihydrotestosterone formate have been developed but have not been marketed. Derivatives Synthetic derivatives of androstanolone (DHT) that have been developed as AAS include: Non-17α-alkylated derivatives Marketed Bolazine (an azine dimer prodrug of drostanolone) Drostanolone (2α-methyl-DHT) Epitiostanol (2α,3α-epithio-DHT) Mepitiostane (a 17-ether prodrug of epitiostanol) Mesterolone (1α-methyl-DHT) Metenolone (1-methyl-δ1-DHT) Stenbolone (2-methyl-δ1-DHT) Never marketed 1-Testosterone (dihydroboldenone; δ1-DHT) Mesabolone (a 17-ether prodrug of δ1-DHT) Prostanozol (a 17-ether prodrug of 17α-demethylstanozolol) 17α-Alkylated derivatives Marketed Androisoxazole (a 2,3-isoxazole A ring-fused derivative of 17α-methyl-DHT) Furazabol (a 2,3-furan A ring-fused derivative of 17α-methyl-DHT) Mebolazine (an azine dimer prodrug of methasterone) Mestanolone (17α-methyl-DHT) Oxandrolone (2-oxa-17α-methyl-DHT) Oxymetholone (2-hydroxymethylene-17α-methyl-DHT) Stanozolol (a 2,3-pyrazole A ring-fused derivative of 17α-methyl-DHT) Never marketed Desoxymethyltestosterone (3-deketo-17α-methyl-δ2-DHT) Methasterone (2α,17α-dimethyl-DHT) Methyl-1-testosterone (methyldihydroboldenone; 17α-methyl-δ1-DHT) Methylepitiostanol (2α,3α-epithio-17α-methyl-DHT) Methylstenbolone (2,17α-dimethyl-δ1-DHT) History Androstanolone was first discovered and synthesized in 1935 by Adolf Butenandt and his colleagues. It was first introduced for medical use in 1953, under the brand name Neodrol in the United States, and was subsequently marketed in the United Kingdom and other European countries. Transdermal androstanolone gel has been available in France since 1982. Society and culture Generic names When used as a drug, androstanolone is referred to as androstanolone () or as stanolone () rather than as DHT. Brand names Brand names of androstanolone include Anaboleen, Anabolex, Anaprotin (), Andractim (formerly AndroGel-DHT) (, , ), Androlone, Apeton, Gelovit (), Neodrol, Ophtovital (), Pesomax (), Stanaprol, and Stanolone, among others. Availability The availability of pharmaceutical androstanolone is limited; it is not available in the United States or Canada, but it is or has been available in certain European countries, including the United Kingdom, Germany, France, Spain, Italy, Belgium, and Luxembourg. The available formulations of