Antibiotics in inflammatory arthritis and background population one year before and after diagnosis: a nationwide drug utilisation study

To describe antibiotic use in patients with inflammatory arthritis (IA) and in the background population (BP) within one year before and after IA diagnosis. Using data from Danish nationwide registries, we identified all adults with a first-time diagnosis of rheumatoid arthritis (RA), psoriatic arthritis (PsA), or ankylosing spondylitis/spondyloarthritis (AS/SpA) from 2010 through 2018. For each IA patient, we randomly sampled ten persons from the BP, matched on sex and birthdate. We calculated the prevalence (n [%]) of any antibiotic dispensing and the total antibiotic dispensing in the year before and after diagnosis. We identified 28 504 new-onset IA patients (RA, n = 16 130; PsA, n = 5,988; AS/SpA, n = 6,386) and 285 040 BP individuals. The one-year prevalence of any antibiotic dispensing was 42.1% in IA patients before diagnosis vs 30.7% in the BP. The total antibiotic dispensing was higher the one-year before both RA, PsA, and As/SpA compared with BP (prevalence rate ratios [PRR], 1.48 [1.46; 1.51]; 1.67 [1.62; 1.72]; 1.52 [1.47; 1.56], respectively), and increased with 22% in IA patients three months before diagnosis compared with the preceding three-month period. Although the prevalence of any antibiotic dispensing in IA patients decreased in the year following the diagnosis (IA; 40.6%), the total one-year antibiotic dispensing remained constant in RA (PRR 0.99 [0.97; 1.01]), decreased in PsA (0.91 [0.87; 0.94]), and increased in AS/SpA (1.08 [1.04; 1.12]) patients after diagnosis compared with before. Antibiotics are more frequently dispensed to individuals developing IA compared with the BP. Antibiotic utilisation patterns change after IA diagnosis with marked differences among IA subgroups.