**2. Prevalence of ADR in older adults**

ADR is defined as "an appreciably harmful or unpleasant reaction resulting from an intervention relating to the use of a medicinal product" [5]. Compared with younger patients, patients aged 65 years or older are seven times more likely to have an ADR requiring hospitalization [6]. ADRs are responsible for 5–28% of acute geriatric hospital admissions, and studies have indicated that more than half of them are preventable with only 19–28% of ADRs causing hospital admission in older patients considered unavoidable [7].

A study done by Harugeri et al. [8] in a hospital setting found that the prevalence of ADR-related hospital admissions was 5.9%, while in another study [9] in India, it was observed to be 6.7%. In-hospital incident ADRs cause a 9% increase in length of stay and a 20% increase in the cost of care encompassing bed consumption, laboratory, and treatment costs [10]. About 20% of ADR-related hospitalizations need blood products to treat gastrointestinal bleeding adding to extra cost on the patient [11].
