Adverse drug reactions & their risk factors among Indian ambulatory elderly patients

Several studies have reported adverse drug events ranging from 5 to 35 per cent in all age group from outpatient setting. However, adverse drug reactions (ADRs) particularly among a large sample of ambulatory elderly patients in India has not been reported. This study has attempted to identify ADRs and assessed their causality, preventability and severity, and also their risk factors in Indian ambulatory elderly patients.

A 2 year long term prospective study included 4005 ambulatory elderly patients (60 yr or above; either sex) at a public teaching hospital. Suspected ADRs were assessed for causality, preventability and severity using Naranjo's probability scale, modified Schumock and Thornton's criteria, and modified Hartwig's criteria, respectively.

Of the total 4005 prescriptions, 406 were identified with ADRs, giving the occurrence of 10 per cent ADRs in elderly. The total number of ADRs was 422 in 406 prescriptions. Type A ADRs accounted for 46 per cent of the total ADRs. Majority of the ADRs (88.6%) were classified as 'probable'. The definitely preventable reactions were 22 per cent. The percentage of moderate reaction was 16 per cent. Only 1.6 per cent ADRs was severe in nature. The most common type of ADR was peripheral oedema. The most commonly offending class of drug was cardiovascular drugs (57.6%). Using logistic regression analysis, the risk factors which contributed to ADRs were age above 80 yr (OR=1.7), prescription of multiple drugs (OR=1.8), longer duration of treatment (OR=2.28) and multiple diagnoses (OR=1.8).

In this study, 10 per cent ambulatory elderly patients were found to have ADRs. This indicates that the elderly patients should be closely monitored for ADRs, to avoid clinically significant harmful consequences. The awareness of risk factors of ADRs would help physicians to identify elderly patients with greater risk of ADRs and, therefore, might benefit from ADRs monitoring and reporting programme.