Drug dosing in patients with renal impairment

Abstract

Inappropriate prescribing (IP) is common in patients with poor renal function in hospital and in outpatient settings. The extent of IP among patients with impaired renal function varies between countries and medical specialities. The aim of this study was to assess the prevalence of IP in a 400-bed acute care hospital and to identify drug classes which are inappropriately prescribed. This study was divided into three main stages. The initial stage was a comparison of medication dosing regimens for chronic kidney disease in medication information sources (British National Formulary [BNF], The Renal Drug Handbook [RDH], UpToDate® [UTD]), which was followed by the development of a medication dosage adjustment guideline for the hospital. The third stage of the study was a retrospective descriptive study that included patients 18 years and older admitted to East Tallinn Central Hospital (ETCH), in Estonia, for more than 24 hours with documented estimated glomerular filtration rates (eGFR) less than 60 ml/min/1.73m2. Patients were selected using stratified random sampling. Medication data and eGFR was collected from electronic health records. The level of agreement for medication dosage adjustments according to renal function between the three sources was less than 50% (46.5%, 44.1%, and 39.6% for BNF, RDH, and UTD, respectively) from 202 recommendations for 71 medications. The guideline developed for the hospital consisted of 54 medications. For the assessment of IP, the study included 399 patients (63% female; 37% male) with an average age of 79 (range 42-99) years. At least one inappropriate prescription was present for 236 (59.1%) patients and 90 patients (38.1%) received ≥3 inappropriately prescribed medications. The prevalence of IP according to eGFR was 32.0% (n=790) with 15% of the prescriptions (n=115) contraindicated in patients with renal impairment. Anticoagulants (n=261, 43.6%) were the most inappropriately prescribed class of medication followed by analgesics (n=85, 33.9%) and antihyperglycemic agents (n=55, 39.6%). Male gender, diabetes, venous thromboembolism, acute kidney injury, length of hospitalisation and surgery performed during hospitalisation were considered to be predictors of IP. The results of the study provide insight for prescribing in patients with renal impairment in hospital settings. IP was a frequent problem among patients with impaired renal function at ETCH. Patients with renal impairment could benefit from a medication dosage adjustment guideline.