DIGOXIN DOSE ADJUSTED ACCORDING TO ESTIMATED CREATININE CLEARANCE IN ELDERLY PATIENTS WITH CARDIAC DISEASE

Background: The precise digoxin dose appropriate for elderly patients with cardiac disease has been unclear, although 0.0625 mg, 0.125 mg, o r 0.25 mg daily have all been used as maintenance dosages. It is gener ally accepted that the dosage should be adjusted depending on the leve l of creatinine clearance. We investigated which level of digoxin (mai ntenance dosage of 0.125 mg or 0.25 mg daily) was appropriate for init iating therapy in elderly patients with cardiac disease based on creat inine clearance level. Methods: The study population comprised 162 eld erly patients with cardiac disease. The formulae to estimate creatinin e clearance were derived from gender, body weight, and serum creatinin e. Furthermore, 24 patients treated medically for cardiac disease who took digoxin without clinical symptoms of digitalis intoxication were used for establishing the relationships between serum digoxin concentr ation (SDC) and estimated creatinine clearance as well as between SDC and measured creatinine clearance. From these relationships digoxin do se necessary to obtain therapeutic SDC was calculated using creatinine clearance. Results: The following equations were derived to predict S DC from measured creatinine clearance and from estimated creatinine cl earance in the patients who took 0.125 mg digoxin daily: SDC = 1.35 - 0.008 x measured creatinine clearance; SDC = 1.36 - 0.008 x estimated creatinine clearance. Conclusions: A maintenance dose of 0.125 mg digo xin should be prescribed for patients with creatinine clearance less t han 70 mL/min, measured or estimated, and 0.25 mg should be prescribed for patients with higher creatinine clearance levels in order to achi eve therapeutic levels of SDC.