Comparison of medigoxin and digoxin in the control of atrial fibrillation.

1 Medigoxin (Lanitop) 300 microgram/day and digoxin (Lanoxin) 500 microgram/day were compared in cross-over studies on healthy volunteers and on patients with uncontrolled atrial fibrillation. Serum glycoside concentrations were measured by radioimmunoassay and ventricular rates by ECG. The two regimens appeared to be therapeutically equivalent. 2 The mean serum glycoside concentration in the steady state and the rate at which this state was attained were similar with both drug regimens in the healthy volunteer group. The between-subject variation in serum glycoside concentration was not significantly less during medigoxin administration. 3 The renal clearance of serum glycoside was much lower during medigoxin administration both in healthy volunteers and in patients. This was not due to a difference in serum protein binding. The relatively small dosage requirement for medigoxin was attributed partly to a lower clearance rate and partly to more nearly complete absorption. 4 During the first 2 weeks of the patient study there was a substantial rise in mean serum glycoside concentration and a corresponding fall in ventricular rate. This was attributed to more consistent self-administration of digoxin. The subsequent change to medigoxin had no further effect on mean glycoside concentration, ventricular rate or frequency of ventricular ectopic beats. 5. An attempt to compare the onset of the ventricular rate response to a single oral dose of medigoxin with that to digoxin gave inconclusive results.