Influence of Gender on the Tolerability, Safety, and Efficacy of Quinidine Used for Treatment of Supraventricular and Ventricular Arrhythmias.

Quinidine, a class IA antiarrhythmic drug (AAD), has been used for the treatment of arrhythmias since the early 1900s. Use has decreased recently because of the availability of newer AADs and concerns about side effects and safety. Quinidine can cause QT prolongation, and women have longer QT intervals and are more susceptible to torsades de pointes (TdP) than are men. We sought to evaluate the influence of gender on quinidine tolerability, safety, and efficacy. We performed retrospective analyses of patients at our institution prescribed quinidine as an AAD between 2000 and 2012. Time to quinidine discontinuation and arrhythmia recurrence were evaluated using Cox proportional hazards models. In 179 patients, 23.5% were women and median age was 65.8 years. Quinidine indication was supraventricular arrhythmias in 68.7% and ventricular arrhythmias in 27.9% of patients. At 3 years after quinidine initiation, Kaplan-Meier probability of quinidine discontinuation was 65.7% for men and 82.4% for women (p = 0.015). Women were more likely than men to discontinue quinidine for QT prolongation (14.3 vs 4.4%, p = 0.036) and TdP (4.8 vs 0%, p = 0.054). After multivariate adjustment, female gender remained independently associated with quinidine discontinuation (adjusted hazard ratio 1.97, p = 0.014). Gender had no influence on arrhythmia recurrence: 1 year after quinidine initiation, Kaplan-Meier probability of freedom from recurrent arrhythmia was 62.4% in men and 57.9% in women (p = 0.33). Quinidine is highly effective in both genders. However, women are more likely than men to experience QT prolongation and TdP on quinidine and are more likely to discontinue quinidine independent of these side effects.