Evaluation of urinary dihydrocodeine excretion in human by gas chromatography–mass spectrometry

Urinary metabolic pattern after the therapeutic peroral dose of dihydrocodeine tartrate to six human volunteers has been explored. Using the GC–MS analytical method, we have found that the major part of the dose administered is eliminated via urine within the first 24 h. However, the analytical monitoring of dihydrocodeine and its metabolites in urine was still possible 72 h after the dose was administered. The dihydrocodeine equivalent amounts excreted in urine in 72 h ranged between 32 and 108% of the dose, on average 62% in all individuals. The major metabolite excreted into urine was a 6-conjugate of dihydrocodeine, then in a lesser amount a 6-conjugate of nordihydrocodeine (both conjugated to approximately 65%). The O-demethylated metabolite dihydromorphine was of a minor amount and was 3,6-conjugated in 85%. Traces of nordihydromorphine and hydrocodone were confirmed as other metabolites of dihydrocodeine in our study. This information can be useful in interpretation of toxicological findings in forensic practice.