NEW YORK (Reuters Health) Jul 29 - Increasing the dosage of infliximab from 3 mg/kg to 5 mg/kg did not significantly reduce symptoms among rheumatoid arthritis (RA) patients who were incomplete responders at the lower dose, according to the findings of a randomized, double-blind study by researchers in the Czech Republic.
Because the increase in infliximab did lead to a moderate increase in toxicity, the authors point out that "there are other alternatives to infliximab when treatment is ineffective. For example, patients may be switched to another anti-TNFa agent, to rituximab or to abatacept."
The study findings are reported in the August issue of the Annals of the Rheumatic Diseases.
The 141 patients in the study had received infliximab 3 mg/kg for 12 months, with methotrexate, and had shown some response, but had not gone into remission. Partial response was defined as a decrease in the disease activity score in 28 joints (DAS28) of more than 1.2 compared with baseline.
Between August 2003 and April 2005, study participants were randomized to intravenous infliximab every 8 weeks at 3 mg/kg or 5 mg/kg. All participants also received methotrexate.
The DAS28 score improved mildly in both groups, but there was no significant difference between the two at the end of 52 weeks or at any intermediate time point. Further, no differences were seen in any of the DAS28 components or secondary endpoints, such as swollen or tender joints or C-reactive protein level.
Although infliximab was generally well tolerated in the study, non-serious adverse events were more common in the higher-dose arm (47.8%) than in the lower-dose arm (28.2%) (p = 0.023).
The researchers caution that their results apply to this specific setting, and do not necessarily apply to other settings or subpopulations of patients with RA.
Ann Rheum Dis 2009;68:1285-1289.
Hmmm, that flies in the face of intuitive and/or conventional thinking, which would seem to indicate if a partial response was experienced at 3mg/kg then a better, and bigger, response would be seen at 5mg/kg.