Identifying Influences on Metabolization of Opioids

A recent study examines the possibility of using laboratory-based testing to identify genetic polymorphisms that affect the way an individual metabolizes opioids in order to aid the selection of treatment for addicts or for patient pain management. Authored by seven researchers from the Medical College of Wisconsin (Milwaukee, USA), the study was presented at the annual meeting of the American Association for Clinical Chemistry (AACC) in Orlando (FL, USA).

Individuals can exhibit a wide range of responses when exposed to identical doses of opiate- or morphine-based drugs. This class also includes methadone and oxycontin, which are used in addiction treatment and pain management. An individual response to these drugs can only be assessed after the drug has been administered, so caregivers have to guess how much to give to achieve the intended effect.
The researchers suggest that pharmacogenetic testing may be a way to help drug-treatment centers select appropriate treatment regimes for addicts and also provide information that could help doctors select appropriate levels for pain management.Scientists know that the toxicity of the synthetic narcotic methadone is affected in part by a patient's metabolism of the drug. Methadone is metabolized by enzymes CYP 1A2, CYP 2D6, and CYP 3A4. The enzyme CYP 2D6 is unique in that it is also a key to the metabolism of other opioids, such as codeine and tricyclic antidepressants.

In the study, the authors conclude that complex medical and prescription histories often make it difficult to conclude that a CYP 2D60-encoded enzyme deficiency is the sole cause of a methadone mortality, or even contributed to death. Nor would the results of genotyping investigations have prompted a change in the ruling of the medical examiner. Yet they believe the study is an important first step in the effort to link genotyping with individual responses to treatment therapies such as methadone, and that establishing this relationship will have a great impact on drug-abuse treatment and pain management.




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