Objective: To estimate biologic drug effects on risk of demyelinating events in rheumatoid arthritis (RA).
Methods: Case-control analyses, nested in an administrative database cohort.
Results: Initially, risk of demyelinating events appeared increased after anakinra drug exposure, and decreased after anti-TNF agents. However, this apparent differential risk was due to more anakinra use (and avoidance of anti-TNF agents), in persons at high risk for demyelinating events. In individuals not at high risk, the adjusted rate ratio after anti-TNF exposures was 1.31 (95% CI 0.68, 2.50) and after anakinra, 0.80 (0.29, 2.24).
Conclusions: When accounting for differential prescription patterns, we noted a trend towards more events after anti-TNF exposures. When studying rare but important potential drug associations, pharmacoepidemiologic studies are valuable but must be carefully-done.