Adverse drug reaction profile of oseltamivir in Indian population: A prospective observational study

Objectives: To analyze the pattern of adverse drug reactions (ADRs) of oseltamivir and its comparison with available data.
Materials and Methods: Suspected or confirmed cases of H1N1 influenza A on therapeutic regimen and close contacts of cases H1N1 influenza A on prophylactic regimen of oseltamivir were included. Data were collected by personal interview after obtaining written informed consent. Causality, severity, and preventability assessments were done by using Naranjo′s scale, modified Hartwig and Siegel′s scale, and modified Schumock and Thornton Scale, respectively. Data were expressed in proportions. Frequency of ADRs in therapeutic and prophylactic groups were compared with phase III trial of oseltamivir by using Chi-square test.
Results: Total 294 patients were interviewed. In prophylactic group, 107 of 257 (41.63%) and in therapeutic, group 23 of 37 (62.16%) developed ADRs. ADRs reported in therapeutic group was significantly (P = 0.029) higher as compared with prophylactic group. Frequently observed ADRs in both the groups were gastritis, nausea, vomiting, diarrhea weakness, sedation, loneliness, sadness, headache, and abdominal pain. Naranjo′s algorithm showed all ADRs in probable category in prophylactic group, 27.78% probable and 72.22% possible reactions in therapeutic group. Severity assessment showed 76% mild and 24% moderate reactions in therapeutic group, 89% mild and 11% moderate reactions in prophylactic group. Severity of ADRs was significantly higher in therapeutic group. Most of ADRs were in nonpreventable category, except gastritis, nausea and vomiting were in definitely preventable category.
Conclusion: Oseltamivir is well tolerated in Indian population. Gastrointestinal side effects are most common and preventable.