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BioMed Research International
Volume 2014, Article ID 702701, 8 pages
Clinical Study

Monitoring Drug and Antidrug Levels: A Rational Approach in Rheumatoid Arthritis Patients Treated with Biologic Agents Who Experience Inadequate Response While Being on a Stable Biologic Treatment

1Department of Rheumatology and Internal Medicine, “Sfanta Maria” Hospital, Bulevardul Ion Mihalache nr 37-39, 011172 Bucharest, Romania
2“Carol Davila” University of Medicine, Bucharest, Romania
3Biology Faculty, Bucharest University, Bucharest, Romania
4Biology Faculty, “Alexandru Ioan Cuza” University, Iasi, Romania

Received 28 February 2014; Revised 7 May 2014; Accepted 7 May 2014; Published 20 May 2014

Academic Editor: Frank Buttgereit

Copyright © 2014 Diana Mazilu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Clinical response in patients with rheumatoid arthritis (RA) treated with biologic agents can be influenced by their pharmacokinetics and immunogenicity. The present study evaluated the concordance between serum drug and antidrug levels as well as the clinical response in RA patients treated with biological agents who experience their first disease exacerbation while being on a stable biologic treatment. 154 RA patients treated with rituximab (RTX), infliximab (IFX), adalimumab (ADL), or etanercept (ETN) were included. DAS28, SDAI, and EULAR response were assessed at baseline and reevaluated at precise time intervals. At the time of their first sign of inadequate response, patients were tested for both serum drug level and antidrug antibodies level. At the next reevaluation, patients retreated with RTX that had detectable drug level had a better EULAR response () with lower DAS28 and SDAI scores ( and ). The same tendency was observed in patients treated with IFX and ETN regarding EULAR response ( and ), DAS28 score ( and ), and SDAI score ( and ). Detectable biologic drug levels correlated with a better clinical response in patients experiencing their first RA inadequate response while being on a stable biologic treatment with RTX, IFX, and ETN.