[Plasma level studies of quinidine retard, their significance for dosage and onset of effect]

A new sustained-action preparation of quinidine-bisulfate (BM-Chinidin Retard) was investigated in 21 patients. After a single oral dose of 1 g peak plasma levels are reached within 3-4 hours with an unsubstantial decrease during the following 4 hours. After 2 g in three divided doses within 12 hours maximal plasma levels are found after 14-16 hours, but an effective level is reached as early as 4 hours after the first dose. With 1 g Chinidin retard given in two doses within 24 hours, varying plasma concentrations are reached after 24 hours, reaching a maximum after 48 hours and decreasing to a medium level thereafter. The minimal concentrations measured were 23 percent lower than the maximal concentrations suggesting that during longterm application rather stable plasma levels are achieved. The effectiveness of the preparation was demonstrated in patients with atrial fibrillation and flutter, supra-ventricular and ventricular premature beats. Longterm treatment was attempted in all patients. Quinidine effectiveness and plasma concentrations were constant throughout the observation period. Side effects were rare: inappetence, vertigo, and headache were observed transiently in 4 patients without necessitating a change in medication. ECG-alterations occurred as described for quinidine-prepartions in general.