Determination of constituents of Telazol®—tiletamine and zolazepam by a gas chromatography/mass spectrometry-based method

Tiletamine and zolazepam injection (Telazol®) is used in veterinary surgical practice to induce short-term anesthesia and also to immobilize wild animals. The present work describes a sensitive method to measure tiletamine and zolazepam concentrations in plasma by means of GC/EI–MS on a 5% phenyl/95% methylpolysiloxane column. A simple liquid extraction procedure with ethyl acetate was used to isolate the two compounds and the same were separated and analyzed by GC/MS without derivatization. A formal validation of the assay demonstrated good accuracy and precision for both tiletamine (98–100.8%; C.V.total < 6.7%) and zolazepam (98.3–103.4; C.V.total < 13.2%). With 500 μl of plasma, the limits of quantification for both tiletamine and zolazepam were found to be 10 ng/ml. Both compounds were stable after three freeze-thaw cycles. The assay was used to analyze plasma samples collected from a pig after intramuscular administration of 10 mg/kg of Telazol®. The plasma concentration–time profile of tiletamine and zolazepam from this representative pig is also provided.