Adverse Drug Reactions: Recognition, Causality Assessment, Reporting and Prevention – A Narrative Review

Abstract

Adverse drug reactions (ADRs) are unintended and harmful responses associated with medicines used at normally recommended doses and remain an important challenge to safe and rational pharmacotherapy. Although pre-marketing clinical trials provide essential information on efficacy and common safety outcomes, uncommon, delayed and population-specific reactions may become apparent only after wider clinical use. Effective pharmacovigilance therefore requires continuous detection, assessment, documentation, reporting and prevention of medicine-related harm. This narrative review summarizes the concept and classification of ADRs, epidemiology and clinical burden, patient- and medicine-related risk factors, mechanisms and manifestations, causality assessment, severity, seriousness and preventability, pharmacovigilance systems, ADR detection and reporting, the Pharmacovigilance Programme of India (PvPI), management, prevention and risk minimization, the role of pharmacists and patient education. The traditional Type A–F classification remains useful for organizing clinical reasoning, while structured approaches such as the Naranjo algorithm support consistent causality assessment. Reporting does not require absolute certainty; a well-documented suspicion may contribute to signal detection when reports accumulate. Modern pharmacovigilance increasingly combines spontaneous reporting with active surveillance, electronic health records, targeted monitoring, and data mining and risk-based approaches. Pharmacists have an important role in medication review, recognition, counselling, documentation and reporting. Strengthening reporting culture, standardized documentation, interprofessional communication and patient participation can reduce preventable harm and improve medicine safety.

Keywords: Adverse drug reaction; Pharmacovigilance; Causality assessment; Naranjo algorithm; ADR reporting; Patient safety; Pharmacist; PvPI.