Overdose rate of drugs requiring renal dose adjustment: data analysis of 4 years prescriptions at a tertiary teaching hospital.

Objective: To determine the overdose rate of drugs that require renal dose adjustment and factors related with overdose.

Subjects: Total of 23,635,210 records of prescriptions and laboratory data of inpatients at a tertiary teaching hospital for the period from January 2002 to December 2005.

Methods: A clinical data mart was constructed. A knowledge base containing dose adjusting information about 56 drugs was built. One day dose was compared to the reference dose adjusted to the patient's renal function.

Results: Considering the patient's renal function, 5.3% of drug doses were excessive. The overdose rate in the patients with moderate to severe renal insufficiency was 28.2%. Only 25% of physicians were responsible for 50.6% of the overdoses. Of 56 drugs studied, 10 drugs, including ranitidine, amoxicillin, and piperacillin/tazobactam, were involved in 85.4% of the overdoses. The physicians with high overdose rate had patients with more impaired renal function (correlation coefficient = 0.192, P < .001). There were negative correlation between clinical experiences of physician and overdose rate (correlation coefficient = -0.221, P < .001) and workload of prescription (correlation coefficient = -0.446, P < .001), when excluding interns from the analyses. There was positive correlation between workload of prescription and overdose rate (correlation coefficient = 0.361, P < .001).

Conclusion: A clinical data mart was useful to analyze the vast amount of electronic hospital data. Drug overdose is quite common among inpatients with renal insufficiency. Only a few drugs are responsible for most of drug overdoses. The physicians' clinical experience, workload of prescriptions, and patients' renal function are correlated with drug overdose.