Background & Summary

Polypharmacy (i.e., the concomitant use of multiple medications in an individual) has become a common phenomenon in the Western world. In the United States, between 2015 and 2018, it has been estimated that two out of three people over 65 take at least three prescription medications during the course of a month (up from one third in the early 1990s), with four out of ten taking five or more medications1. As life expectancy is increasing around the world, leading to more people living with multiple chronic diseases, together with new medicines being launched onto the market each year, giving rise to a growing volume of possible drug combinations, the implications of drug-drug interactions (DDIs) in clinical practice have become a matter of concern. A DDI can lead to the potentiation or antagonism of one drug by another, or cause another effect that is not related to the individual drug profiles. From a mechanistic perspective, DDIs are classified into two main categories: pharmacodynamic and pharmacokinetic2. Predicted DDIs based on pharmacological knowledge (i.e., possible drug effect alterations caused when multiple drugs are simultaneously administered) far outnumber those with clinically significant consequences, i.e., those ranging from lack of efficacy to serious and life-threatening adverse reactions3. The necessarily limited time and extent of pre-clinical studies and pre-marketing clinical trials may burden the identification of adverse drug reactions (ADRs) caused by single drugs or drug combinations (i.e., adverse DDIs).

Postmarketing safety surveillance (pharmacovigilance) is a vital stage in the lifecycle management of a medicine: The number of people exposed to medicines after marketing is substantially larger than the number of volunteers involved in pre-market clinical trials. Spontaneous reporting system (SRS) databases, such as the US Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS), are a particularly useful source of information, with more recent efforts focusing on the integration of multiple data sources4,Full size image