Objective: The objectives of the present study were to determine the prevalence of Potentially Inappropriate Medications and Adverse Drug Reactions in older adults and to collect doctors' responses regarding the PIM list or any other criteria to treat older adults in India. Methods: This was an observational study conducted in different tertiary care hospitals of two districts, Erode and Salem after obtaining approval of the Institutional Ethics Committee. A sample of 250 older adults (60 y and

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... above) and 97 doctors were included during the study period of 6 mo from February 2019 to July 2019. Inappropriate medications were identified by using 2019 updated Beer's criteria. The causality of the adverse events was assessed by Naranjo Adverse Drug Reaction Probability Scale. Results: Out of the 250 prescriptions, only 86(34.4%) of the prescriptions were appropriate and 164(65.6%) were inappropriate. The most commonly inappropriate prescribed medications were diuretics, ranitidine, and tramadol. A total of 74 ADRs was observed in 74 patients. Of these, 57(22.8%) ADRs were due to inappropriate medications listed in Beers criteria. There was a significant association between the occurrence of ADRs and the use of PIMs listed in 2019 updated Beer's criteria [χ2 = 6.08, P = 0.013 (df = 1)]. Conclusion: The study shows that there is a high prevalence of inappropriate medications and adverse drug reactions in hospitalized older adults. Beer's criteria can be used as a guideline by the physicians while prescribing the drugs to the geriatric population.