OBJECTIVES: To study the rationale of early prescription of antibiotics in case of patients with Organophosphorus poisoning. METHODS: In this study patients admitted to the ICU due to organophosphorus poisoning during a six-month period were included. Patients were grouped into group-A and group-B on the basis of antibiotics prescribed and not prescribed respectively. The prescription of antibiotics was classified as prophylactic, empirical and definitive depending on the time of prescription. The effect of antibiotic prescription on the length of stay, cost and clinical outcome was observed. The cost of treatment was obtained from the finance department of the hospital. The length of stay and cost of treatment for the two groups were compared using the non-parametric Mann-Whitney U test. RESULTS: There were 54 patients categorized in three groups according to the severity of poisoning as mild (22%), moderate (48%) and severe (30%). Antibiotics were prescribed for 74.07% of the patients. Prophylactic antibiotics were prescribed in 53.7% cases. The median cost of treatment for group-A patients was INR 60,216 and for group-B patients was INR 27,225 (p=0.001). The median length of stay for group-A and group-B was 14 days and 10 days respectively (p=0.011). The median cost of treatment for moderately poisoned patients prescribed with prophylactic antibiotics was INR 74595.6 as compared to INR 30,902 for moderately poisoned patients of group-B (p<0.05). CONCLUSIONS: Early prescription of antibiotics without any evidence of infection in case of organophosphorus poisoning patients showed a higher cost of treatment and inferior outcomes as compared to OPP cases where a prophylactic antibiotic was not prescribed. The use of higher antibiotics in these cases also lead to increase in antibiotic resistance. There is a need to revise the antibiotic prescription guidelines in case of Organophosphorus poisoning patients.