Introduction: Cardiac patients are generally treated with cardiac medications but, when they develop other common conditions, they may have to be given the necessary non-cardiac medications. There are few such medications which, when given to the cardiac patients produces a potentially lethal drug interaction. Aim: The main aim of the study was to evaluate the prescription of non-cardiac medications that could cause QT interval prolongation among cardiac patients. Materials and methods: The medical records of 100 cardiac patients were collected from both the outpatients and inpatients of cardiology department. The list of medications prescribed to each subject was recorded and classified as cardiac and non-cardiac medications. The ECG changes reported in the literature for both cardiac & non-cardiac medications were collected. Frequency analysis of these medications having effect on QT interval was analyzed. Results: Among the 100 cardiac patients, there were 70 males and 30 females. 86 of them were inpatients and 14 were outpatients. Majority of the patients (63%) were in the age group between 51-70 years. Aspirin (80%) and paracetamol (20%) were found to be the most commonly prescribed cardiac and non-cardiac medications respectively. Conclusion: Many cardiac patients received non-cardiac medications which are known to cause changes in ECG. Hence, wherever possible these medications should be replaced by an appropriate alternative drug which does not cause ECG changes. In situations where prescription of these medications becomes unavoidable, they should be used with caution in recommended doses and for the optimal period to prevent adverse cardiac effects.