Codeine is a prodrug metabolized by ortho-demethylation to morphine. Approximately 8 per cent of the Caucasian population are poor metabolizers, and this percentage is increased by medications such as fluoxetine. Absorption by the intramuscular route is variable, with a fivefold difference in peak blood concentration and a ninefold variation in minimum effective analgesia concentration. Codeine is not a suitable analgesic for the critical care patient.
Tramadol is an atypical opioid which is an agonist for p receptors and inhibits uptake of serotonin and norepinephrine (noradrenaline), producing less sedation and respiratory depression.
Was this article helpful?