ABSTRACT

Objective: To estimate the effects of biological drugs on the risk of demyelinating events in rheumatoid arthritis (RA).

Methods: Case–control analyses nested in an administrative database cohort.

Results: Initially the risk of demyelinating events appeared to be increased after exposure to anakinra and decreased after exposure to antitumour necrosis factor (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 was 1.31 (95% CI 0.68 to 2.50) after exposure to anti-TNF agents and 0.80 (95% CI 0.29 to 2.24) after exposure to anakinra.

Conclusions: When accounting for differential prescription patterns, there was a trend towards more events after exposure to anti-TNF agents. When studying rare but important potential drug associations, pharmacoepidemiological studies are valuable but must be carefully performed