Retrospective evaluation of potentially inappropriate prescribing in hospitalized patients with renal impairment

Background/aims: Patients with chronic kidney disease require appropriate adjustment of nephrotoxic and renally cleared medications to ensure safe and effective pharmacotherapy. It is currently unclear how often appropriate medication selection and dosage adjustment occurs in practice. Therefore, this study aimed to evaluate the extent of potentially inappropriate prescribing (PIP) (the use of a contraindicated medication or inappropriately high dose according to the renal function) in patients with renal impairment from admission through to discharge from the Royal Hobart Hospital (RHH), Tasmania, Australia; to evaluate the medications most commonly implicated in PIP; and the factors associated with PIP in renal impairment.

Methods: Medical records of 251 patients consecutively admitted to the RHH aged 40 years and above, with a creatinine clearance of ≤60 mL/min, and hypertension and/or diabetes mellitus in their medical history, were reviewed. PIP was assessed using the Australian Medicines Handbook and/or product information.

Results: Of the 251 patients, 81 (32.3%) were receiving a total of 116 potentially inappropriate medications (PIMs) at the time of admission. The number of patients receiving PIMs (81 vs. 44, p<0.001 chi-square test) as well as the total number of PIMs (116 vs. 63, p<0.001 Wilcoxon signed rank test) were significantly decreased at discharge. Metformin was the most common PIM at admission. However, PIP of metformin was reduced by approximately 50% by discharge. Logistic regression analysis revealed two significant independent risk factors for PIP: a higher number of medications at admission increased risk of PIP (OR 1.1, 95% CI 1.02-1.18, p=0.010), and higher initial estimated glomerular filtration rate (eGFR) decreased the risk of PIP (OR 0.9, 95% CI 0.96-0.99, p=0.011).

Conclusions: Despite the limitations of lack of body weight documentation and lack of clear guidelines for dosage adjustment based on the eGFR, PIP in patients with renal impairment is common and admission to the hospital was associated with a significant reduction in PIP. More recognition of chronic kidney disease in the community and strategies to alert clinicians of the need for dosage adjustment in renal impairment are warranted.