My patient is taking high doses of morphine – why is codeine positive?
Codeine is not reported in the literature as a metabolite of morphine. While it is not reported in the literature as a known metabolite of morphine, we must not forget that the literature reports primary and secondary metabolites. Codeine, may in fact be a “trace” metabolite for certain individuals on high doses of morphine. Once you reach a high enough level of the parent drug, some of the trace level metabolites reach a level that is detectable. A more likely explanation is that codeine is a minor impurity in pharmaceutical morphine. Again, at lower levels of morphine, this trace impurity goes undetected. However, at higher levels of morphine the codeine impurity is now at a level that we can detect.
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- My patient is taking high doses of morphine - why is codeine positive?
