[Relationship between quinidine plasma level and clinical effect for a new quinidine retard-formulation (author's...

To convert atrial fibrillation 19 patients (8 male and 11 female) were administered (5-vinyl-2-quinuclidinyl)-(6-methoxy-4-quinolyl)-methanol, a new slow-release quinidine formulation (Chinidinorm), containing 250 mg quinidine bisulphate x 4 H2O per tablet, corresponding to 200 mg quinidine sulphate or 164 mg quinidine base respectively. After careful titration of the effective dosage sinus rhythm could be obtained in 17 patients and auriculo-ventricular rhythm in one patient. The drug failed only in one female patient for the occurrence of diarrhoea. Minimum as well as maximum quinidine levels measured in plasma correlated significantly to the quinidine dosages/kg b.w. administered. Part of the quinidine concentrations measured in plasma was at or under the minimum effective levels, respectively, in literature. According to our results it should therefore be discussed to slightly reduce the lower limit of efficacy for plasma quinidine levels. The new quinidine formulation proved to be effective and poor of side-effects with little variations in effective plasma level. Therefore it is to be considered equivalent to all quinidine retard-formulations on the market at present.