Renal function estimations and dose recommendations for dabigatran, gabapentin and valaciclovir: a data simulation...

Area of Science:

• Geriatric Medicine
• Pharmacology
• Nephrology

Background:

• Dabigatran, a thrombin inhibitor, is primarily eliminated by the kidneys.
• Accurate estimation of renal function is crucial for safe and effective drug dosing in the elderly.
• Previous clinical trials utilized the Cockcroft-Gault (CGold) equation and the Modification of Diet in Renal Disease (MDRD4) equation to estimate renal function.

Purpose of the Study:

• To investigate discrepancies in renal function estimation between the CGold and MDRD4 equations in elderly participants.
• To determine if these differences lead to erroneous dabigatran dose recommendations and potentially explain reported bleeding events.
• To compare the impact of these equations on the dosing of other renally excreted drugs, gabapentin and valaciclovir.

Main Methods:

• A retrospective data simulation study was conducted.
• Elderly participants (≥65 years) from six different studies were included.
• Renal function was estimated using the CGold equation (based on uncompensated creatinine) and the MDRD4 equation (based on standardized compensated creatinine).

Main Results:

• A total of 790 elderly participants (mean age 77.6 years) were analyzed.
• MDRD4 estimated significantly higher renal function (eGFR 59.6 ml/min/1.73 m²) compared to CGold (eCrCl 44.2 ml/min) (p<0.001).
• MDRD4 resulted in higher recommended doses for valaciclovir (+21%), dabigatran (+25%), and gabapentin (+37%). Notably, 58% of women would receive a full dabigatran dose with MDRD4 versus 18% with CGold.

Conclusions:

• The MDRD4 equation leads to higher recommended drug doses in the elderly compared to the CGold equation, particularly impacting women.
• This discrepancy increases the risk of dose- and concentration-dependent adverse reactions, including potentially fatal bleeding.
• It is critical to ascertain which renal function estimation method underpins drug product information to avoid overtreatment and ensure patient safety when prescribing renally excreted medications.