Drug Interactions in Palliative Care

PURPOSE: This review of drug interactions in palliative care examines the relevant literature in this area and summarizes the information on interactions of drugs, nutrients, and natural products that are used in the palliative care setting. Particular emphasis is placed on describing the newer information on the cytochrome P450 (CYP) system and the interactions of opioids, antidepressants, and the antitussive, dextromethorphan. METHODS: We performed a search of the MEDLINE database of the time period from 1966 until April 1998, using medical subject headings such as the names of selective serotonin reuptake inhibitors and other relevant medications in palliative care. Literature reviewed included both human and animal articles as well as non-English literature. Bibliographies of these articles and the personal libraries of several palliative care specialists were reviewed. Software developed by The Medical Letter-The Drug Interaction Program was also used. RESULTS: Drug interactions can be categorized in several ways. Drug-drug interactions are the most well known and can be kinetic, dynamic, or pharmaceutical. Pharmacokinetic interactions can involve CYP 2D6, which acts on drugs such as codeine and is responsible for its conversion to morphine. Poor metabolizers, either genotypic or due to phenocopying, are at risk for undertreatment if not recognized. Pharmacodynamic interactions with dextromethorphan may produce serotonin syndrome. CONCLUSION: Drug interactions are important in palliative care as in other aspects of medicine. These interactions are similar to those seen in other areas of medical care but have significant consequences in pain management. Failure to recognize these interactions can lead to either overdosing or undertreatment.