title: Importance of measuring testosterone in enzyme-inhibited plasma for oral testosterone undecanoate androgen replacement therapy clinical trials.
abstract: OBJECTIVE
  Testosterone undecanoate (TU) is metabolized by nonspecific esterases in blood to testosterone (T). Typical clinical practice has been to analyze testosterone in human serum. The degradation of TU to testosterone was evaluated in conditions typically used in clinical studies.
  
  
  RESULTS
  Freshly collected whole blood was fortified with TU at known concentration. Serum was prepared and T concentration was determined by LC-MS/MS. It was observed that TU degrades extensively to T in human blood under conditions typical of harvesting serum causing overestimation of T concentration of up to 243%. These results were confirmed in a clinical study in which serum and plasma samples were compared.
  
  
  CONCLUSIONS
  It was demonstrated that T must be analyzed in enzyme-inhibited plasma when TU is the administered medication.
authors.affiliation: inVentiv Health clinical, Québec, Canada; inVentiv Health clinical, Québec, Canada.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Lachance
authors.affiliation: SOV Therapeutics, Morrisville, NC, USA; SOV Therapeutics, Morrisville, NC, USA.
authors.forename: Om
authors.initials: O
authors.lastname: Dhingra
authors.affiliation: SOV Therapeutics, Morrisville, NC, USA; SOV Therapeutics, Morrisville, NC, USA.
authors.forename: James
authors.initials: J
authors.lastname: Bernstein
authors.affiliation: inVentiv Health clinical, Québec, Canada; inVentiv Health clinical, Québec, Canada.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Gagnon
authors.affiliation: inVentiv Health clinical, Québec, Canada; inVentiv Health clinical, Québec, Canada.
authors.forename: Caroline
authors.initials: C
authors.lastname: Savard
authors.affiliation: inVentiv Health clinical, Québec, Canada; inVentiv Health clinical, Québec, Canada.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Pelletier
authors.affiliation: inVentiv Health clinical, Québec, Canada; inVentiv Health clinical, Québec, Canada.
authors.forename: Nadine
authors.initials: N
authors.lastname: Boudreau
authors.affiliation: inVentiv Health clinical, Québec, Canada; inVentiv Health clinical, Québec, Canada.
authors.forename: Ann
authors.initials: A
authors.lastname: Lévesque
keywords: enzyme inhibitor; hydrolysis; method validation; testosterone; testosterone undecanoate