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.