Objective The administration of the usual dosage of medication in elderly patients with renal impairment can cause adverse drug reactions due to patients' decreased renal function. Using retrospective prescription analysis, in a teaching hospital, this study aimed to evaluate medication dosing errors in elderly patients with renal impairment and the risk factors for these dosing errors. Materials and methods This retrospective study included elderly patients with a creatinine clearance of 59 mL/min or less who were hospitalized in a teaching hospital between July 1, 2015, and September 30, 2015. Data including the patients' age, gender, weight, serum creatinine, duration of hospital stay, and discharge prescriptions were obtained from electronic medical records. Patients with dosing errors were identified, and the risk factors for the dosing errors were statistically analyzed. Results Out of 497 patients, 164 (33%) had evidence of dosing errors. All metformin prescriptions (n = 38) were associated with dosing errors (100%), and trimetazidine was prescribed 11 times in cases where it was contraindicated (31%). The following were confirmed to be statistically significant risk factors that increased the likelihood of the dosing errors: the patient's age (odds ratio (OR): 1.050, 95% confidence interval (CI): 1.011 - 1.092), the number of drugs prescribed per patient (OR: 1.106; 95% CI: 1.012 - 1.210), and the number of drugs requiring dosing adjustments in patients with renal impairment (OR: 1.996; 95% CI: 1.614 - 2.468). Conclusion There was a considerable rate of dosing errors in hospitalized elderly patients with renal impairment. It is necessary for healthcare professionals to make appropriate dosage adjustments in elderly patients with renal impairment to improve the outcomes of pharmacotherapy and patients' quality of life. .
