Objective: To confirm the antimalarial drug induced increase of creatinine to determine the factors contributing to this effect.
Methods: Patients with rheumatoid arthritis (RA) (n = 118) who have used or still use antimalarials (chloroquine or hydroxychloroquine). Serum creatinines prior to antimalarials and serum creatinines during antimalarials were recorded and the creatinine clearance was estimated.
Results: The mean creatinine clearance decreased from 99 ml/min to 92 ml/min (p < 0.001) after the start of antimalarial drugs. Fifty-five percent of the patients with chloroquine compared to 15% of the patients with hydroxychloroquine (chi 2 = 17.8; p < 0.001) had more than 10% decrease of the creatinine clearance. Age (beta = 0.004; p = 0.0002) and the kind of antimalarial (beta = 0.095; p = 0.0002) were strong independent predictors of the decrease of the creatinine clearance in the multiple regression analysis. For patients using chloroquine the mean age adjusted decrease of creatinine clearance was 11.2%.
Conclusion: Antimalarials cause a significant reduction of the creatinine clearance. The use of chloroquine and older age were associated with decreased creatinine clearance. Whether antimalarials affect glomerular filtration or tubular excretion of creatinine remains to be investigated.