Drug-Drug Interactions (DDIs) in Psychiatric Practice, Part 7: Relative Receptor Binding Affinity as a Way of Understanding the Differential Pharmacology of Currently Available Antipsychotics.

Abstract

This column is the seventh in a series exploring drug-drug interactions (DDIs) with a special emphasis on psychiatric medications. The first 3 columns in this DDI series discussed why patients being treated with psychiatric medications are at increased risk for taking multiple medications and thus experiencing DDIs, how to recognize such DDIs, strategies for avoiding and/or minimizing adverse outcomes from such DDIs, and pharmacokinetic considerations concerning DDIs in psychiatric practice. The fourth and fifth columns in this series presented a pair of parallel tables, one of which outlined the primary, known mechanism(s) of action of all commonly used psychiatric medications and one of which summarized major types of pharmacodynamic DDIs based on mechanism of action. Clinicians can use these 2 tables together to predict pharmacodynamically mediated DDIs. The sixth column discussed key pharmacodynamic interactions involving ethanol, opioids, and monoamine oxidase inhibitors. That column focused particularly on hypertensive crises and serotonin syndrome with monoamine oxidase inhibitors and also DDIs involving psychiatric medications with adverse effects on the cardiovascular system and on the central nervous system. This seventh column in this series presents the concept of relative receptor binding and includes a table summarizing the relative receptor binding affinity of commonly used antipsychotic medications, including all of the newer agents as well as some of the older agents such as haloperidol. The overall goal of this series of columns is to present a simple way of conceptualizing neuropsychiatric medications in terms of their pharmacodynamics and pharmacokinetics to allow prescribers to take these facts into consideration when they need to use ≥2 drugs in combination to optimally treat a patient.