A 62-year-old man on long-term oral therapy for ventricular arrhythmias develops arthralgia, pleuritic chest pain, and a positive antinuclear antibody test with anti-histone antibodies. Which antiarrhythmic is most likely responsible?

• A Procainamide ✓
• B Lignocaine
• C Quinidine
• D Mexiletine

Explanation

Drug induced lupus with anti-histone antibodies is the classic adverse effect of procainamide, occurring in up to a third of slow acetylators during prolonged therapy. Quinidine can also cause lupus but far less frequently, and it more typically produces cinchonism with tinnitus, headache and QT prolongation. Lignocaine and mexiletine are not associated with lupus. Slow acetylator status increases susceptibility because the parent drug, not the metabolite, drives the syndrome.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.