en داروسازی بالینی Clinical Pharmacy پژوهشي Original Research <strong>Background</strong>: Resistance to antibiotics, including aminoglycosides &nbsp;(AMG) is one of the problems associated with inappropriate administration of broad-spectrum antibiotics. Objectives: This study aimed to assess the clinical features of aminoglycosides consumption based on the Defined Daily Dose (DDD) index in open heart surgery.<br> <strong>Methods</strong>: This study was done on 268 patients who underwent heart surgery during 2015 and 2016. Clinical and demographic characteristics, laboratory data, and aminoglycoside-related data such as dose and the total duration of administration were collected through a questionnaire designed by the authors. The patients&rsquo; DDD/100 bed-days were calculated, too.<br> <strong>Results</strong>: Out of 268 patients, 170 patients (63.4%) were male. The Mean&plusmn;SD age of the patients was 60.65&plusmn;10.71 years and the Mean&plusmn;SD duration of hospitalization was 12.19&plusmn;7.02 days. Ischemic heart disease was the most prevalent cause of hospitalization. The Mean duration of receiving aminoglycosides was 3.61 days. In 134 patients (50%), creatinine clearance was less than 60 mL/min during aminoglycosides administration. In 25 patients (9.32%), a 50% increase in serum creatinine during receiving aminoglycosides was observed. Creatinine clearance had not been calculated for any patient.<br> <strong>Conclusion</strong>: In this study, monitoring the side effects of aminoglycosides and the serum concentration was not routinely performed. Dose adjustment of aminoglycosides based on renal function test was not considered in a large number of patients and as a result, the dose was inappropriate in many patients. Therefore, it is recommended that the guidelines of drug usage were followed and the patients were monitored more closely for side effects. Intensive Care Units (ICU), Rational use, Cardiac surgery, Microbial resistance, Prophylactic antibiotic, Aminoglycosides, Defined Daily Dose (DDD) 105 114 http://pbr.mazums.ac.ir/browse.php?a_code=A-10-287-2&slc_lang=en&sid=1 Golpar Gholizadeh Shirdarreh 10031947532846005197 10031947532846005197 No Department of Clinical Pharmacy, Cardiovascular Research Center, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran. Gohar Eslami 10031947532846005198 10031947532846005198 Yes Department of Clinical Pharmacy, Cardiovascular Research Center, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran. Aria Soleimani 10031947532846005199 10031947532846005199 No Department of Anaesthesiology, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran. Ebrahim Salehifar 10031947532846005200 10031947532846005200 No Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran.