Objective: To determine the prescription patterns of antiarrhythmic drugs and variables associated with their use in a population of patients affiliated with the Colombian Health System. Methods: A cross-sectional study was performed on a population database with patients who received antiarrhythmics from March to May 2016. Sociodemographic, pharmacological and comedication variables were included. SPSS-24 was used for data analysis using X2 tests and multivariate analyses. Results: In total, 2772 patients were treated with antiarrhythmics in the evaluated period. The mean age was 70.1 ± 13.1 years, and 51.2% were women. In total, 79.4% used a β-blocker, 58.5% amiodarone and 2.9% a calcium channel blocker. Moreover, 1192 (43.0%) patients were prescribed a single antiarrhythmic, and 1580 (57.0%) received two or more. There were 2603 patients (93.9%) with comedication, including lipid-lowering drugs (62.6%), inhibitors of the renin angiotensin aldosterone system (62.6%) and antiplatelet drugs (42.0%). Age older than 65 years increased the probability of comedication (odds ratio [OR]: 2.48; 95% confidence interval [95% CI]: 1.59-3.85), and the risk was proportional to age. We identified 1364 patients treated with conditional risk medications for QT prolongation (49.2%), 68 with a possible risk (2.5%) and 171 (6.2%) with a known risk. Conclusion: Antiarrhythmic drugs recommended by clinical practice guidelines are mainly used; however, risk interactions of QT prolongation were identified and should be taken into account by physicians to avoid adverse events or complications.