Discrepancy Between Equations Estimating Kidney Function in Geriatric Care: A Study of Implications for Drug Prescription.

BACKGROUND: In older patients, the agreement is low between creatinine clearance estimated with the Cockcroft-Gault equation (eCrCl) and glomerular filtration rate estimated with the Chronic Kidney Disease Epidemiology Collaboration equation (eGFRCKD-EPI ). The implications of these discrepancies for drug prescription have so far been assessed only for a few selected molecules.

OBJECTIVE: The aim of this study was to investigate the proportion of geriatric patients receiving drugs with a different recommended dose or indication (i.e. an adjustment discrepancy) depending on eCrCl versus eGFRCKD-EPI estimates of kidney function.

METHODS: Patients admitted to acute geriatric care units in our university hospital were eligible for inclusion. All drug classes were studied. We retrospectively determined recommended prescriptions according to eCrCl and eGFRCKD-EPI .

RESULTS: Sixty percent of patients received at least one drug requiring dose adjustment and/or received a drug with a relative contraindication based on their estimated kidney function. Thirty-one percent of patients received at least one drug with an adjustment discrepancy: 20% received at least one drug for which the recommended dose differed depending on eCrCl versus eGFRCKD-EPI estimates of kidney function, 4% received a drug with a relative contraindication according to eCrCl but not eGFRCKD-EPI , and 7% received both. Factors independently associated with an adjustment discrepancy were older age and lower weight. Main drug classes involved were benzodiazepines, anticoagulants, and anti-microbial drugs.

CONCLUSION: In acute geriatric care units, recommended drug dose adjustments are frequently discordant according to the equations used to estimate kidney function, notably for benzodiazepines, anticoagulants, and anti-microbial drugs. The consequences for treatment efficacy and safety should be investigated.