Xenobiotic Interactions in Psychopharmacotherapy: Classification and Handling

Abstract

Drug-drug-interactions (DDI) are a major topic in programs for continuous medical education (CME). Lectures on this topic usually attract a great audience. Many physicians are afraid of being trapped in charges with malpractice. The idea that a drug-drug interaction is evidence of medical malpractice supports this notion. Some computer databases accessible via internet feed this anxiety by presenting a red exclamation mark if a “drug-drug interaction” is detected in a patient’s medication. Even worse is to categorize this warning like a traffic light. The medical problem is not the drug-drug interaction (DDI) but the adverse drug effect (ADE) that arises from a drug-drug interaction in the individual patient! DDI belong to routine medical practice, and it is often impossible to avoid them. Moreover, they do not just occur between drugs but between any kind of foreign substances (xenobiotica), such as food as well as legal (tobacco smoke, caffeine, alcohol) and illegal drugs. Therefore, the medical challenge is not to just avoid any interaction. Instead, the physician faces the question how to proceed with drug treatment in the presence of such interactions. Based on their medical education, the physician has to judge first of all by themself whether there is a risk for interactions in the prescription they are planning for an individual patient. The classification of interactions into just seven categories proposed in this chapter might hereby help as a sort of checklist. For information that is more detailed, the physician can then consult one of the databases that address the risk for ADE, such as PSIAC (www.psiac.de) or MediQ (www.mediq.ch). Pharmacokinetic interactions may be easily assessed, monitored, and controlled by therapeutic drug monitoring (TDM). Besides these tools, it is important to keep in mind that nobody knows everything; even physicians do not know everything. So take pride in asking someone who might help. For this purpose, AGATE offers its drug information service AID (www.amuep-agate.de). Just good for nothing are computer programs without any kind of medical basis that judge prescriptions without taking into account a patient’s individual peculiarities. In case these types of programs produce red exclamation marks or traffic lights to underline their judgment, they might even work contrapuntal by just eliciting insecurity and terror.