Background: Drug-drug interaction (DDI) poses a marked risk to the patient’s health outcome and puts an economic burden on health-care system.Objective: The aim of the study was to determine the occurrence of potential DDIs and the association between the number of drugs and DDIs.Methods: A prospective observational case study was conducted for the duration of 3 months from January 2014 to March 2014 in the Inpatient Department of General Medicine, General Surgery, and Orthopaedics of Gandhi Medical College and Hospital, Secunderabad. The patient demographic data were collected by designing a patient profile form and the DDIs were assessed and analyzed using the standard online health-care database.Results: A total of 60 case sheets were analyzed. Of these 60 prescriptions, the potential DDIs showed with a majority being of moderate in severity 73.97% such as that of mannitol and ramipril being the most common drug interaction among the cases collected. At least one potential DDIs were observed in 36.66% of the prescriptions. Age and gender did not have any significant effect on DDIs.Conclusion: Therefore, it was observed that DDIs in inpatients were frequent and pharmacist plays a crucial role in managing medication therapy of patients by collaborating with the health-care professionals to prevent adverse drug reactions. DDIs may not appear to cause a serious health problem to the patients and process of drug therapy, but clinical investigations are required to know the actual consequence of the DDIs.