Background: Digoxin is a frequently prescribed drug in the elderly population. Estimated glomerular filtration rate is widely used to adjust dosages. The HUGE value is a tool for differentiating the presence or absence of chronic kidney disease in elderly patients. We aimed to investigate the usefulness of the HUGE value to predict the initial dose of digoxin in patients aged older than 70 years.
Methods: We reviewed retrospectively the medical records of patients aged older than 70 years with serum digoxin concentrations (SDCs) monitored over a 6-month period (63 patients). A linear regression relating the patient's SDC, maintenance dose of digoxin and the HUGE value was estimated to generate a dosage equation. This equation was validated retrospectively (33 patients) and prospectively (35 patients) in comparison with two existing methods based on creatinine clearance.
Results: An equation (HUGE_DIG) was generated to calculate the initial digoxin dose to reach a specific target SDC. Thus, to achieve a SDC of 0.8 ng/mL: Digoxin (mg/day) = 0.091 - 0.006 x HUGE. After retrospective validation, the calculated digoxin doses with this equation were administered in the prospective phase and we did not observe statistical differences between measured and desired SDCs. Moreover, the predictive performance of our equation was better than that obtained with the compared methods.
Conclusions: We offer a new validated digoxin dosing equation for elderly patients. Our results support the need to perform digoxin dosing in elderly people, bearing in mind the changes in renal physiology secondary to ageing and not merely the estimated glomerular filtration rate.