For most drugs and for most adult patients of average build and height, eGFR is an acceptable estimate of renal function.
However, use of eGFR to guide dosing of direct-acting oral anticoagulants is known to increase the risk of bleeding events as a consequence of overestimating renal function. In patients taking these drugs, the MHRA says creatinine clearance should be calculated using the Cockcroft-Gault formula to determine dosage adjustments.
Creatinine clearance should also be used to determine dosage adjustments for:
- patients taking nephrotoxic drugs (such as vancomycin and amphotericin B)
- elderly patients (aged 75 years and older)
- patients at extremes of muscle mass (BMI < 18kg or > 40kg/m²)
- patients taking medicines that are largely renally excreted and have a narrow therapeutic index (such as digoxin and sotalol)
Prescribers can quickly look up dose adjustments for direct-acting oral anticoagulants in renal impairment using the at-a-glance MIMS guide to NOAC dosages in non-valvular atrial fibrillation.
There are currently four direct-acting oral anticoagulants available in the UK: apixaban, dabigatran, edoxaban, and rivaroxaban.