Methotrexate (MTX) is a cornerstone in the treatment of rheumatoid arthritis. Despite its widespread use, expert opinions differ about the optimal MTX starting dosage to achieve rapid onset of action while averting increased occurrence of adverse effects. Plasma concentrations have not been assessed in previous studies that monitored clinical efficacy.
This study was performed to compare the pharmacokinetic parameters and clinical response of a standard (15 mg) and an accelerated (25 mg) dosing regimen, each administered orally once a week.
This randomized, controlled, double-blind, parallel, single-site study included 19 MTX-naïve patients older than 18 years with rheumatoid arthritis. Patients participated for 16 weeks. Disease activity was assessed using the Disease Activity Score in 28 joints (DAS-28) as the primary outcome parameter. Plasma MTX concentrations were measured using HPLC at weeks 1, 5, 10, and 16. Tolerability was assessed via routine blood analysis (hematology and clinical chemistry) and a patient questionnaire to monitor adverse events. Reported or observed adverse events were recorded along with information about their severity and causal relationship to the study medication.
Nineteen white patients (13 women and 6 men; mean age, 56 years; and mean weight, 74 kg) participated. At study entry, mean (SD) DAS-28-4v (erythrocyte sedimentation rate) was 4.73 (1.02). Health Assessment Questionnaire scores were 1.45 (0.85); for C-reactive protein, 11.45 (10.04) mg/dL; for alkaline phosphatase, 73.58 (19.91) U/L; for aspartate aminotransferase, 23.32 (7.13) U/L; and for creatinine, 0.87 (0.22) mg/dL. Although pharmacokinetic parameters such as AUC and C(max) were significantly higher after the accelerated dosing regimen, clinical activity scores (DAS-28) and inflammation parameters (C-reactive protein) did not indicate a significant benefit of an accelerated starting regimen. Considering toxicity, no elevation in liver function enzymes and no decrease in renal function were observed using the accelerated dosing (statistical significance set at P ≤ 0.05). No serious adverse events were noted. All observed adverse events were classified as study related. Overall, adverse events were noted in 58% of patients. Comparison of the two doses revealed that 60% of patients receiving the standard dosing regimen and 56% of patients receiving the accelerated dosing regimen reported adverse events, the most frequent being gastrointestinal. These events were generally self-limiting.
Differences in clinical response between these two small selected patient groups who received an initial oral dose of either 15 or 25 mg MTX per week did not reach the level of statistical significance. The overall incidence of adverse effects, all classified as study related, was 58%, with 60% of patients receiving the standard dosage and 56% of patients receiving the accelerated dosing regimen reporting adverse effects. However, because of the small sample size, this study was not powered to detect differences in the incidence of adverse events between the two dosing groups. ClinicalTrials.gov identifier: NCT00695188.