Open Access Highly Accessed Research article

Diclofenac does not interact with codeine metabolism in vivo: A study in healthy volunteers

Susanne Ammon1, Claudia Marx1, Christoph Behrens1, Ute Hofmann1, Thomas Mürdter1, Ernst-Ulrich Griese1 and Gerd Mikus2*

Author Affiliations

1 Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany

2 Internal Medicine VI – Clinical Pharmacology and Pharmacoepidemiology, University Hospital, Heidelberg, Germany

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BMC Clinical Pharmacology 2002, 2:2  doi:10.1186/1472-6904-2-2

Published: 27 February 2002



Previously, we have demonstrated a marked inhibition of codeine glucuronidation by diclofenac in human liver tissue homogenate. We therefore aimed to investigate whether diclofenac inhibits glucuronidation of codeine also in vivo in healthy volunteers.


In a randomised, placebo-controlled, double-blind, cross-over study, 12 healthy volunteers received a singe of 100 mg codeine phosphate plus 50 mg diclofenac sodium or codeine phosphate plus placebo. Over a 36 hour period serum concentrations of codeine and its metabolites as well as urinary excretion were analysed using LC-mass spectrometry. Side effects were recorded and analgesic efficacy was determined using the cold pressor test (0–6 h).


A single dose of diclofenac did not alter the formation of codeine-6-glucuronide in healthy volunteers. Metabolic clearance of codeine to morphine was not affected by diclofenac. In terms of side effects, both treatments were well tolerated. Diclofenac did not significantly influence the analgesic effects of codeine in the cold pressor test.


In contrast to recent in vitro data, a single oral dose of diclofenac did not alter the glucuronidation of codeine in healthy volunteers.