androgen ester androgen ester an androgen or anabolic steroid ester is an ester of an androgen/anabolic steroid (aas) such as the natural testosterone or dihydrotestosterone (dht) or the synthetic nandrolone (19-nortestosterone). esterification renders aas into metabolism-resistant prohormones of themselves, improving oral bioavailability, increasing lipophilicity, and extending the elimination half-life (which necessitates less frequent administration). in addition, with intramuscular injection, aas esters are absorbed more slowly into the body, further improving the elimination half-life. aside from differences in pharmacokinetics (e.g., duration), these esters essentially have the same effects as the parent drugs. they are used in androgen replacement therapy (art), among other indications. examples of androgen esters include testosterone esters such as testosterone cypionate, testosterone enanthate, testosterone propionate, and testosterone undecanoate and nandrolone esters such as nandrolone decanoate and nandrolone phenylpropionate. parenteral durations of androgens/anabolic steroids medicationformmajor brand namesduration testosteroneaqueous suspensionandronaq, sterotate, virosterone2–3 days testosterone propionateoil solutionandroteston, perandren, testoviron3–4 days testosterone phenylpropionateoil solutiontestolent8 days testosterone isobutyrateaqueous suspensionagovirin depot, perandren m14 days mixed testosterone estersaoil solutiontriolandren10–20 days mixed testosterone estersboil solutiontestosid depot14–20 days testosterone enanthateoil solutiondelatestryl14–28 days testosterone cypionateoil solutiondepovirin14–28 days mixed testosterone esterscoil solutionsustanon 25028 days testosterone undecanoateoil solutionaveed, nebido100 days testosterone buciclatedaqueous suspension20 aet-1, cdb-1781e90–120 days nandrolone phenylpropionateoil solutiondurabolin10 days nandrolone decanoateoil solutiondeca durabolin21–28 days methandriolaqueous suspensionnotandron, protandren8 days methandriol bisenanthoyl acetateoil solutionnotandron depot16 days metenolone acetateoil solutionprimobolan3 days metenolone enanthateoil solutionprimobolan depot14 days note: all are via i.m. injection. footnotes: a = tp, tv, and tue. b = tp and tkl. c = tp, tpp, tica, and td. d = studied but never marketed. e = developmental code names. sources: see template. pharmacokinetics of testosterone esters testosterone esterformroutetmaxt1/2mrt testosterone undecanoateoil-filled capsulesoral ?1.6 hours3.7 hours testosterone propionateoil solutionintramuscular injection ?0.8 days1.5 days testosterone enanthatecastor oil solutionintramuscular injection10 days4.5 days8.5 days testosterone undecanoatetea seed oil solutionintramuscular injection13.0 days20.9 days34.9 days testosterone undecanoatecastor oil solutionintramuscular injection11.4 days33.9 days36.0 days testosterone buciclateaaqueous suspensionintramuscular injection25.8 days29.5 days60.0 days notes: testosterone cypionate has similar pharmacokinetics to testosterone enanthate. footnotes: a = never marketed. sources: see template. structural properties of major testosterone esters androgenstructureesterrelativemol. weightrelativet contentblogpc position(s)moiet(ies)typelengtha testosterone––––1.001.003.0–3.4 testosterone propionatec17βpropanoic acidstraight-chain fatty acid31.190.843.7–4.9 testosterone isobutyratec17βisobutyric acidaromatic fatty acid– (~3)1.240.804.9–5.3 testosterone isocaproatec17βisohexanoic acidbranched-chain fatty acid– (~5)1.340.754.4–6.3 testosterone caproatec17βhexanoic acidstraight-chain fatty acid61.350.755.8–6.5 testosterone phenylpropionatec17βphenylpropanoic acidaromatic fatty acid– (~6)1.460.695.8–6.5 testosterone cypionatec17βcyclopentylpropanoic acidcyclic carboxylic acid– (~6)1.430.705.1–7.0 testosterone enanthatec17βheptanoic acidstraight-chain fatty acid71.390.723.6–7.0 testosterone decanoatec17βdecanoic acidstraight-chain fatty acid101.530.656.3–8.6 testosterone undecanoatec17βundecanoic acidstraight-chain fatty acid111.580.636.7–9.2 testosterone buciclatedc17βbucyclic acidearomatic carboxylic acid– (~9)1.580.637.9–8.5 footnotes: a = length of ester in carbon atoms for straight-chain fatty acids or approximate length of ester in carbon atoms for aromatic fatty acids. b = relative testosterone content by weight (i.e., relative androgenic/anabolic potency). c = experimental or predicted octanol/water partition coefficient (i.e., lipophilicity/hydrophobicity). retrieved from pubchem, chemspider, and drugbank. d = never marketed. e = bucyclic acid = trans-4-butylcyclohexane-1-carboxylic acid. sources: see individual articles. structural properties of major anabolic steroid esters anabolic steroidstructureesterrelativemol. weightrelativeaas contentbdurationc positionmoietytypelengtha boldenone undecylenatec17βundecylenic acidstraight-chain fatty acid111.580.63long drostanolone propionatec17βpropanoic acidstraight-chain fatty acid31.180.84short metenolone acetatec17βethanoic acidstraight-chain fatty acid21.140.88short metenolone enanthatec17βheptanoic acidstraight-chain fatty acid71.370.73long nandrolone decanoatec17βdecanoic acidstraight-chain fatty acid101.560.64long nandrolone phenylpropionatec17βphenylpropanoic acidaromatic fatty acid– (~6–7)1.480.67long trenbolone acetatec17βethanoic acidstraight-chain fatty acid21.160.87short trenbolone enanthatedc17βheptanoic acidstraight-chain fatty acid71.410.71long footnotes: a = length of ester in carbon atoms for straight-chain fatty acids or approximate length of ester in carbon atoms for aromatic fatty acids. b = relative androgen/anabolic steroid content by weight (i.e., relative androgenic/anabolic potency). c = duration by intramuscular or subcutaneous injection in oil solution. d = never marketed. sources: see individual articles. testosterone undecanoate, an ester of testosterone and one of the most widely used androgen esters.