Newer Antipsychotics: Comparative Review of Drug Interactions

The new atypical antipsychotics are subject to drug-drug interactions with other psychotropic agents or with medications used in the treatment of concomitant somatic illnesses - usually at the pharmacokinetic or pharmacodynamic level. While novel antipsychotics are unlikely to interfere with the elimination of other drugs, coadministration of inhibitors or inducers of the cytochrome P450 isoenzymes responsible for their metabolism may modify plasma antipsychotic concentrations, leading to potentially (clinically) significant effects. Newer antipsychotics have binding affinity at a variety of neurotransmitter receptors and might therefore be involved in pharmacodynamic interactions when given in combination with agents acting on the same systems. Differences in the interaction potential among the current novel antipsychotics may be predicted based on their pharmacokinetic and pharmacodynamic properties. Avoidance of unnecessary polytherapy, knowledge of the interaction profiles of individual agents and careful individualization of dosage based on close evaluation of clinical response and possibly plasma drug concentrations are essential to prevent and minimize potentially adverse drug interactions in patients receiving newer antipsychotics.