Quantification of Zolpidem in Canine Plasma

Problem statement: Zolpidem is a non-benzodiazepine hypnotic agent currently used in human medicine. In contrast to benzodiazepines, zolpidem preferentially binds with the GABAA complex ϖ₁ receptors while poorly interacting with the other ϖ receptor complexes. Recent studies have suggested that ZP may be used to initiate sedation and diminish severe anxiety responses in dogs. The aim of the present study is to develop and validate a new HPLC-FL based method to quantify zolpidem in canine plasma. Approach: Several parameters both in the extraction and in the detection method were evaluated. The applicability of the method was determined by administering zolpidem to one dog. Results: The final mobile phase was acetonitrile: KH₂PO₄ (15 mM; pH 6.0) 40:60 v/v, with a flow rate of 1 mL min^-1 and excitation and emission wave lengths of 254 and 400 nm, respectively. The best extraction solvent was CH₂Cl₂:Et₂O (3:7 v/v), this gave recoveries ranging from 83-95%. The limit of quantification was 1 ng mL^-1. The chromatographic runs were specific with no interfering peaks at the retention times of the analyte. The other validation parameters were in agreement with the EMEA. Conclusion/Recommendations: This method (extraction, separation and applied techniques) is simple and effective. This technique may have applications for pharmacokinetic or toxicological studies.