Uses
Quinidine sulfate dihydrate (cas# 6591-63-5) is the hydrated, sulfate salt of Quinidine (Q685000), a dextrorotatory stereoisomer of Quinine. Antiarrhythmic (class IA). Antimalarial.
General Description
Quinidine sulfate dihydrate is the sulfateof an alkaloid obtained from various species ofCinchona and their hybrids. It is a dextrorotatory diastereoisomerof quinine. The salt crystallizes from wateras the dihydrate, in the form of fine, needlelike, white crystals.Quinidine sulfate contains a hydroxymethyl groupthat serves as a link between a quinoline ring and a quinuclidinemoiety. The structure contains two basic nitrogens,of which the quinuclidine nitrogen is the stronger base(pKa 10). Quinidine sulfate dihydrate is bitter and light sensitive.Quinidine sulfate dihydrates are nearly neutral or slightly alkaline. Itis soluble to the extent of 1% in water and more highly solublein alcohol or chloroform.
Clinical Use
Quinidine sulfate is the prototype of antiarrhythmicdrugs and a class IA antiarrhythmic agent according to theVaughan Williams classification. It reduces Na
+ current bybinding the open ion channels (i.e., state A). The decreasedNa
+entry into the myocardial cell depresses phase 4 diastolicdepolarization and shifts the intracellular threshold potentialtoward zero. These combined actions diminish thespontaneous frequency of pacemaker tissues, depress theautomaticity of ectopic foci, and, to a lesser extent, reduceimpulse formation in the SA node. This last action results inbradycardia. During the spike action potential, quinidinesulfate decreases transmembrane permeability to passiveinflux of Na
+, thus slowing the process of phase 0 depolarization,which decreases conduction velocity. This is shownas a prolongation of the QRS complex of electrocardiograms.Quinidine sulfate also prolongs action potential duration,which results in a proportionate increase in the QTinterval. It is used to treat supraventricular and ventricularectopic arrhythmias, such as atrial and ventricular prematurebeats, atrial and ventricular tachycardia, atrial flutter, andatrial fibrillation.
