testosterone phenylbutyrate testosterone phenylbutyrate testosterone phenylbutyrate, also known as testosterone phenylbutanoate, testosterone 17β-phenylbutyrate, and androst-4-en-17β-ol-3-one 17β-phenylbutyrate, is a synthetic, injected anabolic-androgenic steroid (aas) and an androgen ester – specifically, the c17β phenylbutyrate (phenylbutanoate) ester of testosterone – which was never marketed. it is a prodrug of testosterone and, when administered via intramuscular injection, is associated with a long-lasting depot effect and extended duration of action. testosterone phenylbutyrateclinical dataother namestestosterone phenylbutanoate; testosterone 17β-phenylbutanoate; androst-4-en-17β-ol-3-one 17β-phenylbutyrateroutes ofadministrationintramuscular injectionidentifiers iupac name (1s,2r,10r,11s,14s,15s)-2,15-dimethyl-5-oxotetracycloheptadec-6-en-14-yl 4-phenylbutanoate chemspider58539760chemical and physical dataformulac29h38o3molar mass434.620 g·mol−13d model (jsmol)interactive image smiles c12cc3(ccc4=cc(=o)cc34c)1cc2oc(=o)cccc1=cc=cc=c1 inchi inchi=1s/c29h38o3/c1-28-17-15-22(30)19-21(28)11-12-23-24-13-14-26(29(24,2)18-16-25(23)28)32-27(31)10-6-9-20-7-4-3-5-8-20/h3-5,7-8,19,23-26h,6,9-18h2,1-2h3/t23-,24-,25-,26-,28-,29-/m0/s1key:kpkrhhwuomeerq-mpzzesaysa-n