Rational prescribing means prescribing the more effective and healthiest drug for a disease according to patient’s condition, the type of effective drugs, cost and etc. The non-normative and non-rational prescribing of medicine can cause side effects. Prescribing of effective and safe drugs can have an important role in treatment of patient and the lack of side effect, drug interactions and imposition of additional cost. The aim of this study was to evaluate drug interactions in prescriptions of Lorestan province, western of Iran In this study, at first, the statistic of the insurance prescription of all provincial pharmacies were obtained, interred in the prescription review software of food and drug administration, processed in terms of drug interactions and data were statistically analyzed. This study shows that of the total 1443973 of the prescription numbers, 1112 numbers of that contain 1.25 mg of Digoxin tablets with 40 mg of Furosemide tablets that they have a severe interaction and can lead to arrhythmia in patients. Also 934 prescriptions contain Gemfibrozil and Lovastatin which can lead to myopathy and rhabdomyolysis in consumer patients. The survey revealed that 1.36, 3.76 and 0.56% of prescriptions have mild, moderate and severe interactions, respectively. Existence of severe and moderate drug interactions requires that further workshops be held for physicians on drug interactions.