Individualizing pain therapy with opioids: The rational approach based on pharmacogenetics and pharmacokinetics

A correct long-term opioid therapy implies the selection of the appropriate opioid and dose for each patient, but it is well demonstrated that the “clinical” approach alone is not sufficient. To this purpose, the literature is stressing that physicians have to focalize even more their attention both on the pharmacokinetic and pharmacodynamic properties of the opioids and on the differences among patients, including the genetic background. Accurate and fast analytical methods (e.g. Tandem Mass Spectrometry) for detecting plasma opioid concentrations represent a useful tool for clinicians to prevent adverse reactions in selected patients. The detection of polymorphisms of several genes involved in opioid absorption, distribution, metabolism, and elimination are promising to customize pain therapy. The success of the chronic opioid therapy also depends on the other drugs co-administered, possibly giving origin to drug-drug interactions; the clinical outcome should be constantly monitored.