Cohort study on adverse drug reactions in adults admitted to the medical wards of a tertiary hospital in Nigeria: Prevalence, incidence, risk factors and fatality

Aims Intensive monitoring of medical patients for adverse drug reactions (ADRs) to assess prevalence, incidence, risk factors and fatality of ADRs leading to hospital admission or occurring in the hospital. Methods Prospective cohort study on 1280 adult patients admitted to the medical wards of a tertiary institution over 12 months. Patients were assessed for ADRs during and throughout admission; causality and preventability of ADRs were assessed. Results Sixty-seven (5.2%) patients had ADRs, 51 (3.9%) caused hospitalisation while 17(1.3%) occurred during hospitalisation, and 42 (62.7%) of total ADRs were preventable. Nonsteroidal anti-inflammatory drugs, 14 (20.3%), antidiabetics, 12 (17.4%) and antibacterial, 11 (15.8%) were the most implicated drug classes. Gastrointestinal tract (37%), central nervous system (30.2%), and skin (24.7%) were the most affected organ/systems, while upper gastrointestinal bleeding and hypoglycaemia were the most observed ADRs. ADRs led to deaths in 7 (10.4%) patients, with an overall case fatality rate of 0.5%. The highest number of deaths were among patients with Stevens-Johnson syndrome 2/7 (28.6%) and hepatotoxicity 2/7 (28.6%). Risk factors, adjusted odds ratio (AOR [95% confidence interval, CI]) for ADRs leading to hospitalisation was male sex 3.11 (1.11, 8.73) while for ADRs during hospitalisation were number of drugs used before admission (AOR [95% CI] = 6.67 [1.16, 38.47]) and comorbidities (AOR [95% CI] = 3.0 [1.13, 8.01]). Patients admitted with ADRs had prolonged hospital stay (AOR [95% CI] = 3.37 [1.11, 8.71]). Conclusion Preventable ADRs are common and important causes of hospitalisation and inpatients' morbidity and mortality among medical patients in Nigeria. Upper gastrointestinal bleeding and hypoglycaemia, resulting from nonsteroidal anti-inflammatory drugs and antidiabetic drugs were the most observed ADRs.