Disposition in humans of racemic picenadol, an opioid analgesic

P. M. Franz, S. L. Anliker, J. T. Callaghan, K. A. DeSante, P. H. Dhahir, R. L. Nelson, A. Rubin

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Racemic picenadol is being tested clinically as a analgesic. The (+)-enantiomer of picenadol is an opioid agonist and the (-)-enantiomer is a weak agonist/antagonist. The disposition of racemic [14C]picenadol was studied in healthy men after a single dose was administered im (N = 3) and orally (N = 5). After the dose, virtually none of the radioactivitiy that appeared in blood was associated with the red cells. In plasma, approximately 4% of the radioactivity was attributable to the parent drug, the remainder being picenadol glucuronide (~35%) and other metabolites. The t( 1/2 ) for total radioactivity was 6 hr, that for the unchanged drug was 3.5 hr. Picenadol was present in plasma almost exclusively as the (+)-enantiomer. However, after incubation with glucuronidase and sulfatase, plasma contained 2 to 4 times more (-)- than (+)-picenadol, indicating that more conjugated (-)-picenadol than conjugated (+)-picenadol was in the plasma. After im and oral administration of [14C]picenadol, plasma levels of radioactivity were generally 10 and 70 times higher than those in saliva, respectively. More than 90% of the administered radioactivity was excreted in the urine, mostly as picenadol glucuronide, and lesser amounts of picenadol sulfate and N-desmethylpicenadol sulfate. Only about 1% of the administered dose of picenadol appeared unchanged in urine. The disposition of racemic picenadol in humans was stereoselective, the (-)-picenadol apparently being metabolized preferentially over the (+)-enantiomer. This finding was of particular interest in view of the dissimilar pharmacologic activities of the enantiomers. In a separate multiple dose study of picenadol, the disposition of the drug was found to be similar to that in the single dose study.

Original languageEnglish (US)
Pages (from-to)968-973
Number of pages6
JournalDrug Metabolism and Disposition
Issue number6
StatePublished - 1990

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science

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