Effect of Bariatric Surgery on the Pharmacokinetics of Codeine, Oxycodone and Tramadol-A Case Series

The impact of bariatric surgery on the pharmacokinetics of codeine, oxycodone or tramadol is largely unknown.

In patients treated with these opioids before and after bariatric surgery, serial drug concentrations were measured throughout a dose interval preoperatively and 1, 6 and 12 months postoperatively.

Eight patients treated with codeine (n = 2), oxycodone (n = 2) or tramadol (n = 4) were included. In the patients using codeine, the area under the concentration-time curve during a dose interval (AUC) was moderately increased for the active metabolites morphine and morphine 6-glucuronide 6-12 months after bariatric surgery. For oxycodone, there were only negligible AUC changes. In the tramadol group, there were no discernible AUC changes considered to be caused by the surgical procedure. There were no apparent changes in maximum concentrations or times to achieve maximum concentrations after surgery for any of the drugs or their metabolites.

From a pharmacokinetic point of view, we found no evidence that particular follow-up procedures should be needed for codeine, oxycodone and tramadol in patients undergoing bariatric surgery and continuing drug treatment. However, as always, doses should be adjusted based on clinical effect and the occurrence of adverse drug reactions.