COMPARISON OF THE PHARMACOLOGIC ACTION OF QUINIDINE AND DIHYDROQUINIDINE

¹ From The Lilly Research Laboratories, Eli Lilly and Company, Indianapolis 6

A comparison was made of some pharmacologic actions of pure quinidine, dihydroquinidine, and commercial quinidine sulfate, U.S.P. The following results were obtained:

1. The threshold doses of dihydroquinidine and quinidine required to raise the intensity of electrical stimulation needed to produce ventricular fibrillation in cats were approximately 1 and 3.5 mg. per kg., respectively.

2. In doses of 10 mg. per kg. intravenously into anesthetized cats, quinidine or dihydroquinidine caused a marked fall of blood pressure—almost of equal intensity. The duration of action of quinidine on blood pressure was more prolonged however. Doses of 1 to 2 mg. per kg. intravenously produced only slight and very transient fall of blood pressure.

3. From the median lethal doses obtained by intravenous injection into mice, dihydroquinidine was about 18% more toxic than quinidine.