Psychotropic Drug Interactions

TLDR: This chapter provides an overview of psychotropic drug interactions, and it is vital that physicians understand pharmacologic principles when prescribing more than one drug.

Abstract: Publisher Summary This chapter provides an overview of psychotropic drug interactions. Psychotropic polypharmacy has developed and continued largely out of clinical experience. Physicians have prescribed combinations of drugs in the hope of alleviating clinical symptoms resistant to single medications. Although some drug combinations are desirable and efficacious, most are of limited usefulness and are potentially hazardous. Drug interactions can occur by changes in absorption, excretion, metabolism, or plasma protein-binding effects, and by blocked transport and changes in drug mediator activity. Some drug interactions produce clinical responses directly contrary to those intended; consequently, it is vital that physicians understand pharmacologic principles when prescribing more than one drug. As interactions among most drugs are unknown or only partially known, polypharmacy should be regarded primarily as investigational. Despite the fact that current evidence indicates that most drug combinations are no more effective than drugs used singly, many physicians continue to prescribe polydrug regimens. The rationale behind this practice is that lower doses of two drugs may be more potent therapeutically and may cause fewer side effects than higher doses of one drug. Surveys of prescribing trends, however, indicate that doses of drugs used in combination tend to be higher than doses of the same drugs used individually. Furthermore, two drugs, even at lower doses, appear to cause more side effects than a higher dose of a single drug. Until further research clarifies possible drug interactions, physicians should limit the number of psychotropic drugs administered simultaneously.