Predisposing Factors for Adverse Drug Reactions

Adverse drug reactions (ADRs) are multifactorial phenomena, and predisposing factors for ADRs can be considered components of a constellation of causes, including the drug, needed for an ADR to be induced. The identification of the predisposing factors for ADRs is an important task of pharmacovigilance, as it may contribute to prevent the occurrence of ADRs. There are four types of predisposing factors: (1) those related to patient characteristics (e.g., age, sex, ethnicity, genetics); (2) those related to the underlying diseases or comorbidities (e.g., renal failure, liver disorders, metabolic disorders); (3) those related to environmental and lifestyle factors (e.g., smoking, alcohol consumption, caffeine use); and (4) those related to the concomitant use of other drugs (e.g., drug–drug interactions, polypharmacy). Predisposing factors interact with the drug to increase the risk of presenting an ADR, and the best tools to identify them are analytical epidemiological studies. Through them, it is possible to estimate the measures of a drug–event association and then assess which factors may strengthen such an association. Once a predisposing factor has been identified, it is necessary to translate this information into appropriate regulatory measures in order to minimize the risk of ADRs. In this context, health-care professionals play a crucial role in implementing risk minimization measures, informing patients, and monitoring the results.