Investigation of stability of selective androgen receptor modulators in urine

Selective androgen receptor modulators (SARMs) are a class of new emerging “designer” steroid compounds gaining popularity over more well established anabolic-androgenic steroids (AAS) amongst both non-professional and elite athletes. Moreover, due to their anabolic activity, SARM compounds may also potentially be abused in livestock animals to increase meat production. Consequently, SARM residues should be monitored as a part of routine testing employed within both anti-doping and drug residue laboratories. Since only a limited amount of information on SARM compound stability is currently available within the peer-reviewed literature, this study reports a practical approach to assess optimal storage conditions for 15 SARM compounds in solvent solutions (standard stock and intermediate mixed standard solutions) stored at −20°C for up to 1 year, as well as in a range of urine test matrices (bovine, equine, canine and human) under frozen (−20°C, −80°C) storage for up to 20 weeks and post freeze-thaw cycles. Moreover, SARM storage stability within solvent extracts was assessed at −20°C (0–4 weeks) and 4°C (0–2 weeks). Findings demonstrate that SARM analytes are stable in reference solutions when stored at −20°C, apart from PF-06260414 (stock solution) which should be stored at lower temperatures (e.g. −80°C). A limited degree of compound instability was observed for a number of SARM analytes in urine both when stored at −20°C, and after repeated freeze-thaw cycles. Moreover, SARM compounds within reconstituted urine solvent extracts were found to be effectively stable when stored for up to 4 weeks at −20°C and for 2 weeks at 4°C. The long-term stability testing data reported here will inform the more timely and effective development and validation of analytical methods for SARM residue detection and analysis, ensuring confidence in findings from monitoring of livestock animals and anti-doping processes.