Question

CD21 [Mar98] [Jul98] The antiarrhythmic effect of lignocaine:

A. Because it increases the refractoriness of in cardiac muscle
B. Therapeutic level 2-5ng/ml
C. Class IA antiarrythmic
D. Effective nebulised for laryngospasm
E. Is an ester local anaesthetic

Answer 1

CD21 [Mar98] [Jul98] The antiarrhythmic effect of lignocaine:

C. Class IA antiarrhythmic

Step-by-step explanation:

Lignocaine is a Class IB antiarrhythmic drug, not Class IA. Class IB antiarrhythmics primarily affect sodium channels during depolarization and have a faster onset and offset of action than Class IA drugs. Lignocaine stabilizes cardiac cell membranes by blocking sodium channels, reducing the rate of depolarization and decreasing excitability, making it effective in treating ventricular arrhythmias. The therapeutic level for lignocaine is commonly considered to be 2-5 μg/ml, not ng/ml. Therefore, option C, "Class IA antiarrhythmic," is incorrect.

Intravenous administration of lignocaine is the preferred route for treating ventricular arrhythmias, and nebulized lignocaine is not a common or recommended route for this purpose. Lignocaine's antiarrhythmic effect is not attributed to an increase in refractoriness of cardiac muscle, making option A incorrect. Additionally, lignocaine is an amide local anesthetic, not an ester, eliminating option E.

In summary, the correct answer is C. Class IA antiarrhythmic. Lignocaine is a Class IB antiarrhythmic, and its therapeutic level is in μg/ml, not ng/ml. The drug's antiarrhythmic effects are associated with sodium channel blockade, making it an effective treatment for ventricular arrhythmias.