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. 1997;53(3-4):235-9.
doi: 10.1007/s002280050368.

Polymorphic CYP2D6 mediates O-demethylation of the opioid analgesic tramadol

W D Paar  1 , S Poche, J Gerloff, H J Dengler
Affiliations

Polymorphic CYP2D6 mediates O-demethylation of the opioid analgesic tramadol

W D Paar et al. Eur J Clin Pharmacol. 1997.

Abstract

Objective: This study was designed to investigate whether the in vivo metabolism of tramadol was influenced by CYP2D6 polymorphism.

Methods: The extent of tramadol O- and N-demethylation was calculated by determining the amounts of tramadol and O- and N-desmethyltramadol in 24 h urine after ingestion of a test dose of tramadol. The O- and N-demethylation rates were calculated by dividing the 24-h urinary excretion amount of tramadol by that of O- and N-desmethyltramadol. Volunteers were phenotyped for CYP2D6 polymorphism using sparteine as an in vivo probe.

Results and conclusion: High correlation was found between tramadol-O-demethylation and sparteine oxidation in 71 extensive metabolizers of sparteine (rs = 0.544). The mean metabolic ratio of tramadol O-demethylation was significantly higher in poor metabolizers of sparteine than in extensive metabolizers (4.4 vs 0.8). These in vivo results confirm that tramadol O-demethylation is carried out to a large extent by the polymorphic CYP2D6.

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