Radioimmunoassay of digoxin and measurements of ventricular rate at rest and exercise were performed four times daily during maintenance therapy and following discontinuation of the drug in five patients with atrial fibrillation. No consistent diurnal variation in ventricular rate during maintenance therapy was observed despite fluctuations in plasma digoxin levels. Following withdrawal of the drug, the chronotropic effect persisted longer than would be expected from the plasma elimination rate. Our findings imply that a divided daily dose for the control of atrial fibrillation is not required; a single dose suffices.
Zener JC, Anggard EE, Harrison DC, Kalman SM. Persistence of Digoxin Effect in Atrial Fibrillation. JAMA. 1973;224(2):239-241. doi:10.1001/jama.1973.03220150047013