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Objective

To estimate the incidence and rate of outpatient antibiotic and antiviral medication use among children receiving methotrexate and/or an injectable tumor necrosis factor α (iTNFα) inhibitor (etanercept and/or adalimumab) and to compare these rates with those of a control population.

Methods

Data were obtained from a pharmacy benefit manager (PBM) database. Children were included if they had ≥1 prescription claim for an iTNFα inhibitor or methotrexate prescribed by a pediatric or adult rheumatologist between 2008 and 2010 and if they were age <18 years at the time of the claim. A control cohort of randomly selected children was generated from the PBM database. Poisson regression was used to compare antimicrobial rate ratios (RRs). Incidence rates and RRs were adjusted for age, sex, and prednisone exposure.

Results

In total, 4,312 children were included. The adjusted RRs for antibiotic prescriptions among children receiving methotrexate monotherapy or iTNFα inhibitor and methotrexate combination therapy compared with the control cohort were 2.18 (95% confidence interval [95% CI] 1.92–2.47) and 2.12 (95% CI 1.79–2.50), respectively. The adjusted RRs for antiviral prescriptions among children receiving methotrexate monotherapy or iTNFα inhibitor and methotrexate combination therapy compared with the control cohort were 3.67 (95% CI 1.98–6.78) and 4.34 (95% CI 1.86–10.14), respectively. The RRs for the iTNFα inhibitor group were similar in magnitude. There was no significant difference in RRs between the medication exposure categories for either antibiotic or antiviral prescriptions.

Conclusion

Children receiving methotrexate and/or an iTNFα inhibitor had higher rates of antibiotic and antiviral use compared with the control cohort. Data sets with additional patient-level and disease-specific data are required to assess this association in more detail.