Purpose: to determine the incidence of switching and the factors associated with the switch-free time of brand or generic imatinib. Methods: analytical, dynamic cohort, observational, prospective study, between January-2017 and January-2022. The exposed group was patients with brand drugs and the non-exposed with generic with 83 patients in each group. The dependent variable was switching from imatinib to another drug. Each patient was observed for 12 months. Absolute and relative frequencies and summary measures were used. Kaplan-Meier was performed to calculate switch-free time, spearman correlation, and chi for measurements over time. Differences between measurements were established with Log-Rank-Test and variables with significance were input to a COX proportional hazards model. Results: the median time on treatment in exposed patients was 325 days [RIC 141-365] and in non-exposed patients 365 [RIC 179-365] (p-value: 0.2616). Of those exposed and non-exposed, 20.5% and 26.5%, respectively, had a switch in medication (p-value: 0.4639). The exposed group had a survival of 74.1% [95% CI 64.0%-87.7%], with a mean time to change of 319±11 days. In the non-exposed group, survival was 70.0% [95% CI 60.0%-81.4%] and time 305±12 (p-value: 0.5). No significant differences were identified for any of the independent variables when analyzing crude or adjusted measures of strength of association, but the variables polymedication, history of non-adherence or pharmacological non-persistence behaved as potential risk factors. Conclusion: the incidence of switching between brand-name and generic imatinib was not significant and the factors associated with faster drug switching were polymedication, history of drug nonadherence, and non-persistence with pharmacy drug claims.