ANALYSIS OF ADVERSE DRUG REACTIONS SPONTANEOUSLY REPORTED IN A TERTIARY CARE HOSPITAL AT HOSUR TAMIL NADU, USING WHO-UMC CAUSALITY ASSESSMENT SCALE: A PROSPECTIVE OBSERVATIONAL STUDY

Background: Adverse drug reactions (ADRs) are a global health concern, contributing to morbidity, prolonged hospital stays, and increased healthcare costs. In India, underreporting and inconsistent causality assessment hinder pharmacovigilance. WHO UMC scale standardizes ADR classification; semi urban hospital data remain limited. Objective: To systematically analyze ADRs reported in a semi urban tertiary hospital in Hosur, Tamil Nadu, using the WHO UMC causality assessment scale, and to evaluate their severity, preventability, and drug class distribution. Methods: A prospective observational study was conducted over one year at St. Peter’s Medical College & Hospital. All spontaneously reported ADRs from inpatients and outpatients were included. Data were collected using Pharmacovigilance Programme of India (PvPI) forms and assessed with the WHO UMC causality scale, Hartwig and Siegel severity scale, and Schumock and Thornton preventability criteria. Results: A total of 36 ADRs were documented in patients aged 9 months to 80 years, with slight female predominance. Cephalosporins (42%) were leading, followed by contrast agents (22%) and NSAIDs (11%). Dermatological reactions were most frequent, systemic events linked to contrast agents and opioids. Severity: 50% mild, 33% moderate, 17% severe, several ICU admissions. Preventability: 67% preventable, 33% not. WHO UMC classified most “Probable,” fewer “Possible,” none “Certain.” Conclusion: ADRs in this semi urban hospital were mostly mild and preventable, linked to antibiotics and contrast agents; severe ICU cases demand vigilance, stronger pharmacovigilance, allergy documentation, and clinician awareness.