Introduction: This research paper is based on a study conducted on the in-doorpatients at a teaching hospital in Gujrat, Pakistan, in order to check for the frequency with whichPenicillins, Quinolones and Cephalosporins are being used together and in combinations withother drugs and the drug-drug interactions that occur due to these combinations and theirimpacts on the patients. Objectives: (1) To check the frequency with which Penicillins,Quinolone and Cephalosporins are being used in different combinations in patients. (2) Todetermine their drug-drug interactions. (3) Impact on patients due to these interactions. (4)Reasons for prescription of mismatched combinations by clinicians. Study Design: 270 randomprescriptions were collected from different wards of DHQ hospital, Gujrat. These prescriptionswere then analyzed for drug interactions among the above mentioned group of drugs, with thehelp of soft ware program named The Medical Letter Adverse Drug Interaction Program. Setting:Aziz Bhatti Shaheed Hospital (DHQ), Gujrat , Pakistan. Period: Prescriptions were collected overthe period of 3 months. Conclusions: Prescribing antibiotics for different indications in indoorpatients is unavoidable. However, it is the duty of the clinician to monitor the patient when he isusing two or more drugs together. This study recommends the use of drug-drug interactiondetecting software in hospitals, so that, the level of patients’ safety may be enhanced.