Anticoagulation Myth Busters

MYTH

“My patient is renally impaired, they cannot have an OAC”

REALITY

“The degree to which OAC agents are cleared by the kidney varies, and, as shown by the table below, dose adjustments are necessary at various levels of renal impairment. Care should be taken to consider patients age, weight and renal function prior to deciding the most appropriate agent.

Creatinine Clearance (CrCl)* Warfarin(12) Apixaban(6) Dabigatran(7) Edoxaban(8) Rivaroxaban(9)
≥50 ml/min Closely monitor INR. 5mg twice daily.
Reduce to 2.5mg twice daily in patients with two or more of the following:
• Age ≥80 years
• Body weight ≤60kg
• Serum creatinine ≥1.5mg/dL (133 micromoles/L).
Usual dose is 150mg twice daily.
Consider 110mg twice daily in 75 to 80 year olds, or with moderate renal impairment, gastritis/ GORD or at increased risk of bleeding.
Reduce to 110mg twice daily in patients >80 years, or if taking verapamil.
60mg once daily.
Reduce to 30mg once daily in patients with one or more of the following clinical factors:
• Low body weight <60kg
• Concomitant use of ciclosporin, dronedarone, erythromycin or ketoconazole.
20mg once daily with food.
30 – 49 ml/min Closely monitor INR. Use normal dose. 110-150 mg twice daily. Reduce dose to 30mg daily. Reduce dose to 15mg daily.
15 – 29 ml/min Closely monitor INR. Reduce dose to 2.5mg twice daily. Contra-indicated. Reduce dose to 30mg daily. Reduce dose to 15mg daily.
< 15
ml/min
Closely monitor INR. Contra-indicated. Contra-indicated. Contra-indicated. Contra-indicated.

*calculated using Cockroft-Gault

The Cockcroft-Gault equation is the standard method for estimating creatinine clearance (CrCl) and drug dose adjustment in adults using the patient’s age, weight, sex and serum creatinine. Current CrCl calculators embedded within GP IT systems provide estimated glomerular filtration rates (eGFR), which do not give a reliable estimate of CrCl for the adjustment of NOAC doses and therefore should not be used.

We recommend use of the MD+CALC Cockcroft-Gault equation which recognises the need to adjust for bodyweight in obese patients (BMI >30) and will calculate a modified estimate of CrCl with a range that is based on ideal bodyweight (IBW) and actual body weight (ABW). This can be accessed using the link: https://www.mdcalc.com/creatinine-clearance-cockcroft-gault-equation or it can be downloaded as an app.

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