Drug Interaction or Adverse Drug Reaction? Confusing Terms.
The news item (BMJ 1998;316:1930), while citing a reference(1), mistakingly has ascribed two million American hospitalizations annually to drug interactions instead of adverse drug reactions (ADR). ADRs may include drug interactions as one of many causes but the reverse is not true. The reader is cautioned regarding usage of drug reaction terms as multiple nearly-similar terms of varying granularity abound. Examples of drug interaction terms include adverse drug interaction, drug-drug interaction, drug-laboratory interaction, drug-food interaction, etc.
Drug interaction is defined as, "An action of a drug on the effectiveness or toxicity of another drug". And "An adverse reaction to a drug has been defined as any noxious or unintended reaction to a drug that is administered in standard doses by the proper route for the purpose of prophylaxis, diagnosis, or treatment(2). However, WHO's original definition of ADR excluded therapeutic failures, intentional and accidental poisoning and drug abuse, as well as adverse events due to medication errors such as drug administration or non-compliance(1).
Recently, another more inclusive term, Adverse Drug Event (ADE) has come into use. According to Bates et al, the term ADE, defined as an injury resulting from medical intervention related to a drug, is preferred since it is more comprehensive and clinically significant than the ADR(3).
Due to non-uniform usage of these terms, it is sometimes difficult to compare various studies and derive incidence rates, etc. for ADRs, and Drug Interactions. Let us hope that standardization of these drug-related terms occurs as rapidly as our understanding of these phenomena evolve.
1. Lazarou J, Pomeranz BH, Corey PN. Incidence of Adverse Drug Reactions in Hospitalized Patients. A Meta-analysis of Prospective Studies. JAMA 1998;279:1200-1205.
2. Vervloet D, Durham S. Adverse reactions to drugs. BMJ 1998;316:1511-1514.
3. Bates DW, Cullen DJ, Laird N, et al. Incidence of Adverse Drug Events and Potential Adverse Drug Events. Implications for Prevention. JAMA 1995;274:29-34.
Competing interests: No competing interests