Kidney Week

Abstract: TH-OR91

Performance of eGFR Equations for Drug Dosing in Kidney Transplant Recipients

Session Information

• Onconephrology and Precision Pharmacology
  November 02, 2023 | Location: Room 107, Pennsylvania Convention Center
  Abstract Time: 04:30 PM - 04:39 PM

Category: Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)

• 2000 Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)

Authors

• Hundemer, Gregory L., Ottawa Hospital Research Institute, Ottawa, Ontario, Canada

Gregory L. Hundemer, MD, MPH

• Sood, Manish M., Ottawa Hospital Research Institute, Ottawa, Ontario, Canada

Manish M. Sood,

• Akbari, Ayub, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada

Ayub Akbari,

Background

For kidney transplant recipients (KTRs), drug dosing is most commonly determined by using eGFR as a surrogate for graft function. Which eGFR equation performs best for drug dosing in KTRs remains unknown.

Methods

Cross-sectional study of 415 stable KTRs from Canada and New Zealand with same-day values of serum creatinine and cystatin C along with measured GFR (^99mTc-DTPA). We assessed the performance for drug dosing of CKD-EPI (both indexed to a standardized body surface area [BSA] of 1.73m² [mL/min/1.73m²] and non-indexed to account for actual BSA [mL/min]) and Cockcroft-Gault (via 3 different weights: ideal, adjusted ideal, and actual body weight) eGFR equations relative to measured GFR based upon recommended renal dosing of 8 medications commonly prescribed to KTRs: famciclovir, ganciclovir, trimethoprim/sulfamethoxazole, oseltamivir, ciprofloxacin, levofloxacin, lamivudine, and nimatrelvir/ritonavir. The primary outcome was proportion of drug dosing discordance (under- or over-dosing) overall and stratified by obesity status (BMI < or ≥30kg/m²).

Results

The non-indexed CKD-EPI equations led to a lower proportion of drug dosing discordance compared to the indexed CKD-EPI equations across all study drugs (Figure). The Cockcroft-Gault equations based upon adjusted ideal and actual body weight led to a lower proportion of drug dosing discordance compared to ideal body weight. These findings were most pronounced among obese KTRs. Overall, the non-indexed 2021 CKD-EPI eGFR equations showed the lowest proportion of drug dosing discordance across all study drugs.

Conclusion

When employing eGFR-based drug dosing for KTRs, actual BSA should be accounted for to mitigate the risks of under- or over-dosing. The non-indexed 2021 CKD-EPI equations provide the most accurate eGFR-based guidance for appropriate drug dosing among KTRs.