Objectives: To study the prevalence of adverse drug reactions (ADRs) in five different hospitals of Kathmandu Valley.

Materials and Methods: An analytical cross sectional study was designed from May 2007 to September 2007 in which prevalence of ADR was calculated. A total of 37 cases of ADRs were taken from 4287 patients and 10% of the remaining population without ADRs i.e. 425 out of 4250 patients was selected randomly. ADRs were analyzed as per the structured questionnaires designed by Canadian adverse drug reaction monitoring program. Data thus obtained were analyzed by using SPSS and Excel 2003 software and relevant statistical tools were applied.

Results: Prevalence of ADR in this study was 0.86% and male to female ratio was 0.85. 54.1% were female and 45.9% were male (P = 0.65). The highest percentage of ADRs were seen in adult patients, however the difference was statistically not significant. Maximum numbers of ADRs were reported from skin, 35.13% followed by GIT, 29.72% and then from CNS, 18.91%. Anti-infectives were associated with maximum number of ADRs followed by IV urograffin. Rashes, 35.13% were the most common type of ADRs reported followed by vomiting, 13.51% and then dizziness which was 10.81%. Regarding the outcomes attributed to ADRs, one patient died due to ADR caused by dapsone and 15 cases got hospitalized due to ADRs. The incidence of ADRs in different age groups was not significant. Similarly, there was no significant association between ADRs and sex. No significant difference was seen in case of age group less than one year as compared to two or more years of age (P = 0.78). For causality of ADRs, according to Naranjo algorhythm scale, 35% of reactions were assessed to be probable, 32% as possible and 19% were definite. Similarly, for severity assessment, 54% reports were mild, 35% were moderate and 10.81% were severe.

Conclusion: Prevalence of ADR in this study was 0.8% which is similar to other studies in other countries. All the ADRs were not toxic reactions and they were unpredictable.