Quantification of dextropropoxyphene and its metabolite by HPLC in hair of overdose cases

Hair samples taken from 11 persons suspected to have died from an overdose of legal or illicit drugs were analysed. These hair samples were selected, because classical post-mortem toxicological investigations in blood revealed the presence of dextropropoxyphene (PPX) and its major metabolite norpropoxyphene (NPPX). For the hair analysis, hair strands were cut into segments of about 3 cm, washed with water and acetone, dried and pulverised. An aliquot of about 40 mg of those segments was incubated with acetate buffer pH 4.0 and beta-glucuronidase/arylsulfatase. After liquid-liquid extraction with hexane-3-methylbutanol (99:1), drugs were identified and measured by HPLC using piritramide as an internal standard. Preliminary assays showed that the limit of detection for PPX is below 1.0 ng/mg hair, the limit of detection for the metabolite NPPX being significantly higher (1.5 ng/mg). GC/MS, usually the method of choice for this kind of determination, was not chosen, because of the thermolability of PPX and its unspecific mass spectrum. From the hair of 11 persons, 24 segments were prepared and processed. Our results show that ten persons were found positive for PPX; moreover, when regarding the 24 segments, only three were found negative. PPX and NPPX concentrations were detected at maximal concentrations of 26.4 and 71.0 ng/mg hair respectively. Considering the ratio of PPX to NPPX for each person, we found more PPX than NPPX for three persons, whereas for seven persons we found more of the metabolite than its parent drug.