OBJECTIVES: Adverse drug reactions (ADRs) are known to have a significant impact on the morbidity and mortality in the hospitalised patients. They also pose a considerable challenge on the health care system. Therefore, this study was aimed to characterise the ADRs and to assess their causality, severity and preventability in inpatient department (IPD). METHODS: This prospective observational study was conducted in the patients of either gender, admitted to general wards of medicine department of a public teaching hospital. Those patients were excluded in whom ADR occurred prior to the admission to the ward. The causality of ADRs was assessed using 2 scales - Naranjo’s and WHO-UMC criteria. Severity and preventability were assessed using Modified Hartwig’s severity scale and Modified Schumock & Thornton criteria, respectively. RESULTS: Of 382 patients with complete documentation, 344 did not suffer from any ADR. Only 38 patients experienced ADRs during their stay in hospital (9.9%). A total of 46 ADRs were identified in 38 patients. The three top most classes of drugs involved in ADRs were antimicrobial drugs, diuretics and minerals. Constipation (32%) followed by hypokalemia (21.7%), hypoglycaemia, hypersensitivity reactions were most commonly observed ADRs. 69.5% of ADRs were ‘probable’ and 30.5% were ‘possible’ in nature (Naranjo’s scale). WHO-UMC criteria showed 28.5% of ADRs were ‘probable’ and 71.5% were ‘possible’. As per Modified Hartwig’s severity scale, 34.7% of ADRs were ‘mild’, 60.8% ‘moderate’ and 4.5% were ‘severe’. Using Modified Schumock & Thornton criteria, it was found that 61% of ADRs were ‘probably preventable’, 32.6% were ‘definitely preventable’ and 6.5% were ‘not preventable’. CONCLUSIONS: In this study incidence of ADRs was found to be 9.9%. Majority of these ADRs were ‘probably preventable’ and the authors believe that a regular mechanism to monitor the patients’ and records will be a viable option to minimise the ADRs.