Off-label use of rituximab and associated factors in adult patients: a pilot study
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Background: the description of those characteristics that are associated with the off-label use of monoclonal antibodies remains paramount if we are to maximize the rational use of available resources. Our main objective was to describe the prevalence of off-label use of Rituximab, in addition to its associated factors (for example, prescribing physician and patient´s clinical and socioeconomic characteristics). Methods: we designed a retrospective cross-sectional study which included patients starting treatment with Rituximab between 2010 and 2016. Our main exposure was the time when Rituximab´s patent expired. Other potential factors associated with the off-label prescription pattern were baseline diagnosis and comorbidities in addition to the main characteristics of the prescribing physician. The main outcome was the prevalence of off-label use of Rituximab. We used a multivariate logistic regression model in order to estimate the association between time and our main endpoint. Results: out of 160 eligible patients that started treatment with Rituximab we included 22 adult patients in our main analysis by conducting a random sampling procedure. The prevalence of off-label use was 30.4% (95% CI, 13.9 to 54.9%). We did not find a change in the prescription pattern of Rituximab with regards to time and patent expiration. The only factor associated with off-label use were previous hospitalizations (7 vs. 1, p = 0.04). Conclusions: the off-label use of Rituximab is common in our population. Future studies evaluating distinct factors associated with such use as well as its impact in both potential efficacy and toxicity are warranted
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