Objective: The objective of the study was to evaluate the adverse drug reaction (ADR) related to commonly used antimicrobials in a tertiary care hospital.Methods: A prospective spontaneous reporting study involving, active methods (pharmacist actively looking for suspected ADRs) and passive methods (stimulating prescribers to report suspected ADRs) was carried out in all departments of a tertiary care hospital, for 1 year. Patients of all age groups were included in the study. The data for the study were taken from case sheets, investigation reports of patients who had experienced an ADR, personal interviews with reporting persons or clinicians, personal interviews with patient or patient's attendant, past history of medication use, which were generally obtained from, prescriptions from the past, reports of medical and surgical interventions, referral letters, ADR reporting forms. Collected data were then analyze for causality assessment by Naranjo's scale and severity assessment by Hartwig and Siegel's scale.Result: During 1 year of study period, 75 ADRs related to antimicrobial were reported among 1354 patients who were given antibiotic for the treatment. The incidence rate of antibiotic was found to be 5.53%. The department that reported ADR was medicine (10.16%), ENT (4.6%), pediatric (8.12%), orthopedics (06.9%), surgery (06.9%), chest and tuberculosis (04.6%), obstetrics and gynecology (06.9%), dentistry (02.3%), and skin (10.16%). The most common ADRs were related to gastrointestinal tract; dermatological reactions were second in the list of antimicrobial drugs causing ADR. In this study, among antimicrobials, fluoroquinolones, and beta-lactam antibiotics were the most common drugs causing gastrointestinal and dermatological ADRs. There was no unknown ADR reported that may need to be further investigated through active monitoring. All patients recovered from ADRs without any complications. The causality was assessed by Naranjo's scale and it revealed that out of 75 antibiotics related ADR 48 (64%) were possible, 27 (36%) were probable, 3 (4.00%) were definate, and 0% were unlikely. According to the Hartwig and Siegel's scale, most of ADR were mild 45 (60%) and moderate 30 (40%) in nature.Conclusion: ADRs related to antimicrobials occurs frequently. Among antimicrobials, fluoroquinolones, and beta-lactam antibiotics were the most common drugs causing gastrointestinal and dermatological ADRs. The health-care system can promote the spontaneous reporting of antimicrobial ADR to pharmacovigilance center for ensuring safe drug use and patient care
