To assess the effects of tocilizumab on methotrexate and 7-hydroxymethotrexate pharmacokinetics in patients with rheumatoid arthritis and to explore the pharmacodynamic effect of tocilizumab on C-reactive protein (CRP), a marker of inflammation.
Methotrexate (10 - 25 mg) was administered orally on Days 1, 8, 15, 22, 29, 36, and 43. On Day 8 patients received 10 mg/kg tocilizumab intravenously. Blood samples for pharmacokinetic analyses were collected on Days 1, 15, and 43 and for pharmacodynamics (CRP) throughout the study.
90% CIs for mean effect ratios (Day 15/Day 1 and Day 43/Day 1) of methotrexate and 7-hydroxymethotrexate (AUClast and Cmax) were close to or within the bioequivalence boundaries (80 - 125%). CRP normalized within 1 week after tocilizumab injection and remained within normal limits for 3 weeks.
Tocilizumab and methotrexate can be administered concurrently without dosage adjustments.