To Örebro University

Introduction: In the last years B-cell depleting therapies such as rituximab (RTX) have become commonplace in the therapeutic landscape of multiple sclerosis (MS), with this class of drugs showing high efficacy. Nevertheless, B-cell depleting therapies have been associated with a higher risk of bacterial infections compared to other disease modifying therapies.

Objectives/Aims: To report the frequency and type of antibiotic prescriptions during a 10-year period.

Methods: A retrospective cohort study was performed on MS-patients followed at Örebro University Hospital (Örebro, Sweden), having received at least one dose of RTX between 2011 and 2020. The number and types of prescribed antibiotic therapies were registered. Data collection was performed using the Swedish MS-registry and electronic patient files. We registered all prescriptions for antibacterial agents between the first dose of RTX administered and 12 months after the last dose, or until the study cut-off date of December 31, 2020, whichever came first.

Results: A total of 219 patients were included (213 with relapsing-remitting MS; mean age 40 years). The median Expanded Disability Status Scale was 2.0. Median disease duration was 36 months at the start of rituximab, median follow-up time was 43 months, and the median number of rituximab infusions was 6. A total of 415 antibiotic prescriptions were registered in this time period. The mean number of prescriptions per patient and year was 0.5. In the cohort, 115 (47%) of the patients did not receive an antibiotic prescription. The most common type of infection treated was urinary tract infections (UTI), followed by upper respiratory tract ones. The majority (83%) of patients who received antibiotic therapy for UTI were women. There were 16 patients (7%) that required long duration of treatment with antibiotics and 15 (7%) of the study population were hospitalized for infections.

Conclusion: Prescription of antibiotics is frequent among MS-patients treated with RTX, occurring in approximately half of this patient population. UTI is the most common cause of antibiotic treatment.