National assessment of renal estimation for drug dosing among pharmacists

Abstract

Introduction Creatinine‐based equations used to estimate renal function are inaccurate in certain clinical contexts; however, there are limited resources to guide pharmacists in these situations. Objectives To assess current renal function estimation and subsequent drug dosing practices among American College of Clinical Pharmacy (ACCP) members via an electronic survey. Methods A 21‐item survey was emailed to the listservs of four ACCP Practice‐Research Networks: Adult Medicine, Nephrology, Critical Care, and Infectious Diseases. The survey included pharmacist demographics, practice site information, and case‐based clinical application scenarios requiring the respondent to choose a renal function estimate for overweight, underweight, and elderly patients (≥65 years). Four patient cases captured respondents' enoxaparin dosing decisions in patients with an estimated creatinine clearance of around 30 mL/min. Estimates of renal function were provided based on Cockcroft‐Gault (C‐G), Modification of Diet in Renal Disease, and Chronic Kidney Disease Epidemiology equations. Results There were 299 survey responses. The majority of respondents were pharmacists (98%) who practiced in the hospital setting (96%) as clinical specialists (69%). The C‐G equation was chosen to estimate renal function most commonly (85%). Total and adjusted body weights were used in C‐G estimates most commonly in patients who were underweight (80%) and overweight (75%), respectively. Given an elderly patient with low serum creatinine (Scr), 34% of respondents used actual Scr, 30% rounded Scr to 0.8, and 29% rounded Scr to 1.0 for use in C‐G. Enoxaparin renal dose adjustment differed based on clinical indication. Respondents chose more frequent (every 12 hour) dosing in patients with pulmonary embolism vs atrial fibrillation. Of the 79% of respondents whose practice site utilizes pharmacist‐driven renal dose adjustment policies, 94% indicated they deviated from the policy. Conclusion Large variation exists among clinical pharmacists in the application of renal function estimating equations which may impact dosing strategies and patient care.

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“…The CrCl estimated by the CG equation is commonly recommended for drug dosage adjustment 22. The eGFR, especially estimated by the CKD-EPI equation, usually reports in clinical setting for classifying chronic kidney disease and staging of renal function.…”

Clearance Confusion: An Exploratory Analysis of Inpatient Dosing Discordances Between Renal Estimating Equations

“…C-G IBW appears to be the most common method for adjusting renal medications among pharmacists in America based on prior research. 9,10 C-G TBW was the original equation proposed by Cockcroft and Gault and is still used in many industry-sponsored trials that inform package insert recommendations. 4 Recently, literature has been published to suggest that the least-biased variants of the C-G equation vary by patient BMI.…”

“…21 This estimation methodology has been adopted among some pharmacy practitioners and will be defined henceforth as Cockcroft-Gault optimized (C-G Optim ). 10 MDRD and CKD-EPI, adjusted for patient-specific body surface area, are both recommended by NIDDK for drug dosing purposes and are listed for dosing purposes on an increasing number of package inserts. 11 Patient admissions were also assessed for the presence of medications that were on the hospital’s automatic renal dose adjustment policy; these medications include antibiotics, antifungals, antivirals, histamine-2 receptor antagonists, and other medications.…”

“…7,8 Further complicating the issue is the fact that many health care practitioners use different variants of these equations in clinical practice. 9,10 For example, surveys demonstrate that many pharmacists use ideal body weight (C-G IBW ), adjusted body weight (C-G ABW ), or total body weight (C-G TBW ) variations of the C-G equation depending on a patient’s weight or body mass index (BMI); yet individual practices vary widely. 10 Professional organizations, including the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and Kidney Disease: Improving Global Outcomes (KDIGO), do not provide specific recommendations as to which renal estimating equation to use but instead advocate for the use of any of the MDRD, CKD-EPI, or C-G equations for drug dosing purposes.…”

“…9,10 For example, surveys demonstrate that many pharmacists use ideal body weight (C-G IBW ), adjusted body weight (C-G ABW ), or total body weight (C-G TBW ) variations of the C-G equation depending on a patient’s weight or body mass index (BMI); yet individual practices vary widely. 10 Professional organizations, including the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and Kidney Disease: Improving Global Outcomes (KDIGO), do not provide specific recommendations as to which renal estimating equation to use but instead advocate for the use of any of the MDRD, CKD-EPI, or C-G equations for drug dosing purposes. 11,12 Practice variation also exists among pharmaceutical manufacturers whose choice of renal estimating equations in clinical studies informs package insert recommendations.…”