Pharmacokinetics, Pharmacodynamics, and Pharmacogenomics of Opioids

Of late, the realization that unrelieved pain continues to be a prevalent problem despite the availability of effective analgesic agents has encouraged a movement toward establishing a balance between the prevention of drug misuse, abuse, and diversion, and the provision of adequate pain control. In this and other publications, opioids have been acknowledged as essential medications that are necessary for the relief of chronic, pain-inducing conditions. Yet, it is still important to integrate risk management into programs of care and for clinicians to develop skills to minimize risks of misuse, abuse, and diversion of medications. Despite opioids' historical longevity and established place in the armamentarium of analgesics for control of both acute and chronic pain, recent advancements in the field warrant reconsideration of the available data on opioids. For example, developments in pharmacogenomics research have demonstrated that the intrinsic analgesic mechanisms, pharmacokinetics, and metabolism of opioids are dictated by an individual's genetics. This has important clinical ramifications. Because each patient has a unique genetic background, analgesic regimens need to be individualized for each patient to maximize analgesic opioid effects and minimize side effects. Moreover, opioid rotation should be considered when analgesia to a particular pharmacotherapy is inadequate or induces significant adverse effects.