Forensic drug testing for opiates. II. Metabolism and excretion rate of morphine in humans after morphine administration

J. M. Mitchell, B. D. Paul, P. Welch, E. J. Cone

Research output: Contribution to journalArticle


Urine levels of free and total morphine were determined by GC/MS for four male subjects who received single doses of 20 mg of morphine sulfate intramuscularly. Peak concentrations were observed within 10 h for both conjugated and free morphine; thereafter, levels declined rapidly. Initially, free morphine represented from 25 to 34% of the total amount of morphine present, but this ratio declined after 12 h to an average of only 5.9% of total morphine. Free morphine accounted for an overall mean of 6.8% of the dose excreted in urine and conjugated morphine for 58.6%. The mean excretion half-life for free morphine was 6.6 h and for conjugated morphine was 8.2 h. The lower concentration and shorter half-life of free morphine resulted in a shorter detection time for free morphine versus total morphine at a 300-ng/mL cutoff. An equivalent detection time for free morphine was obtained when its cutoff was lowered to 25 ng/mL. The possibility that morphine is metabolized to codeine was unequivocally ruled out by the finding of an absence of codeine at or above the LOD of the GC/MS assay in all clinical specimens collected after morphine administration.

Original languageEnglish (US)
Pages (from-to)49-53
Number of pages5
JournalJournal of analytical toxicology
Issue number2
StatePublished - Jan 1 1991


ASJC Scopus subject areas

  • Analytical Chemistry
  • Environmental Chemistry
  • Toxicology
  • Health, Toxicology and Mutagenesis
  • Chemical Health and Safety

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