Original article25 mg etanercept once weekly in rheumatoid arthritis and spondylarthropathy
Introduction
Anti-TNFα agents like etanercept have been an historical breakthrough in the treatment of rheumatoid arthritis (RA) and ankylosing spondylitis (AS). However, etanercept shares with other anti-TNFα agents concerns about long-term side-effects (including possible increasing incidence of haematological malignancies) [1], [2], and high costs (as compared with classical DMARDs) [3]. A first goal of RA treatment is to achieve major clinical improvement (an ACR50 improvement being more relevant than an ACR20 [4]), without increasing too much the risk of severe side-effects (which are much more feared by RA patients than by their physicians [5], and might be dose-related [6]). Hence, and as marked variations in effectiveness have been noticed across anti-TNFα in individual patients, it seems reasonable to switch patients to another anti-TNFα when the response to a first drug is inadequate [6], [7], [8]. On the contrary, as the response to etanercept can be very pronounced in some patients, it might also be worth to perform a drug titration (step-up or step-down) [9], [10] to avoid too high concentrations of etanercept [11], especially when prevention of structural changes is not a major goal. A same statement could apply to spondylarthropathy. In fact, although dose-finding studies have concluded that etanercept 25 mg twice a week was, on average, the best dosage, several arguments suggest that less frequent injections might already be quite effective at the clinical level for the subset of patients responding well to etanercept (which should be even more true for RA patients treated with a combination of etanercept and a DMARD like methotrexate). Indeed, considerable interindividual variability in the pharmacokinetics of anti-TNFα agents has been reported, including etanercept [12]. As previous reports had also emphasized the possibility of very good results of etanercept 25 mg once a week for nearly half of RA patients [9], [10], we performed a retrospective analysis of the 6 months clinical results of our patients for whom etanercept had been introduced at 25 mg once a week to treat either RA or spondylarthropathy.
Section snippets
Methods
In June 2005, in a rheumatology unit, 112 patients (47 ± 11 years old) had been taking etanercept for at least 6 months: 54 were suffering from rheumatoid arthritis, 37 from ankylosing spondylitis, and 21 had been classified as either psoriatic rheumatism or peripheral spondylarthropathy.
A minority of patients (44/112 or 39%) had been treated by 25 mg etanercept once weekly, either because of their fear of side-effects or the slow worsening of structural changes. The remaining 68 patients (61%) had
Results
Values of DAS-28 just before the initiation of etanercept (DAS28-J0) and after 6 months of treatment (DAS28-M6) were available in 51 patients: 20 from the half-dose group, and 31 from the full-dose group. Values of BASDAI just before the initiation of etanercept (BASDAI-J0) and after 6 months of treatment (BASDAI-M6) were available in 41 patients: 20 from the half-dose group, and 21 from the full-dose group.
In 20/112 (18%) patients (4/44 from the half-dose, and 16/68 from the full-dose) at least
Discussion
Despite the open, not randomised, and retrospective design of this study, the magnitude of the improvement of DAS-28 and BASDAI after 6 months of treatment by etanercept 25 mg once a week (instead of 25 mg twice a week) strongly suggests that such a therapeutic regimen could induce a marked and sustained relief in some patients with rheumatoid arthritis or spondylarthropathy. In fact, although inter-individual plasma concentrations of 79 patients treated with a stable dose of methotrexate plus
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