In a recent study by Guillermo Alberto Keller et al., published in Journal of Opioid Management (, UCT’s Clean Screen® DAU was used to extract Propoxyphene (DPX)  and norpropoxyphene (NPX) from human plasma and analyzed by GC-MS. Plasma samples (500 µl) were treated with a strong alkali hydroxide to form NPX amide and extracted using CSDAU203. The recovery of the procedure was higher than 81%.  Calibration curves were prepared by spiking blank plasma with corresponding analytical solution to obtain calibration concentration of 25, 100, 200, 400, 600, 800 and 1000 ng per mL. Limits of quantification (LOQ) was 25 ng per mL, with linear response over the range 25-1000 ng per mL and correlation coefficients higher than 0.999.

DPX is a synthetic diphenyl heptane analgesic with structural similarity to methadone. There are four propoxyphene stereo-isomers. The alpha dextro-propoxyphene isomer possesses analgesic activity, whereas the levopropoxyphene isomer possesses antitussive activity, with negligible analgesic activity. DPX half-life is 6 to 12 hours in the human, resulting mainly from liver metabolism and excretion through renal and biliary routes. The toxicity of DPX is attributed to its major metabolite, NPX. This metabolite lacks any significant opioid activity, is less of a CNS depressant, and presents a slightly greater local anesthetic effect.