To investigate the efficacy, toxicity and drug discontinuation rate in an observational study of patients with established rheumatoid arthritis treated with infliximab.

Between September 1999 and June 2003, we enrolled 84 patients with rheumatoid arthritis who were being treated with infliximab. All patients met the American College of Rheumatology criteria for rheumatoid arthritis and had been refractory to (or did not tolerate) at least two disease-modifying antirheumatic drugs. Patients entering the study had a negative purified protein derivative skin test, were fully informed about the treatment regimen, and were followed up at predefined times according to a standardized protocol. Data concerning infliximab dosage, tolerability, adverse events, concomitant therapy, dosage interval, and drug discontinuation were all recorded. In addition, the clinical and laboratory variables according to the American College of Rheumatology 20% and 50% response criteria and the disease activity score for the 28 joint indices were also recorded.

There were 61 women and 23 men with a mean age of 59 ± 8 years and mean disease duration of 11 ± 6 years. Seventy—five percent (63/84) were seropositive for IgM rheumatoid factor. After the first year of treatment, 84.5% of patients continued to be treated with infliximab, whereas this percentage was 73% after the second year and 59% after the third year of treatment. The American College of Rheumatology 20% response criteria was met by 59/84 (70%) of patients, and 38/84 (45%) of the patients achieved the 50% response criteria in the first year of treatment. At the second year of therapy, the American College of Rheumatology 20% response criteria were reached by 35/84 (42%) of the patients and the 50% response criteria by 27/84 (32%). At the third year of treatment with infliximab, the American College of Rheumatology 20% and 50% response criteria were achieved by 13/84 (15.5%) and 10/84 (12%) of the patients, respectively. Twenty-eight of eighty-four (33%) patients discontinued infliximab therapy. The risk of drug discontinuation decreased with the concomitant use of methotrexate. The main reasons for drug discontinuation were adverse drug reactions (16/84, 19%), followed by lack of efficacy (9/84, 11%). The main reasons for drug discontinuation due to side effects were immediate hypersensitivity reactions (9/84, 11%) and infections (6/84, 7%).

Infliximab was found to be an alternative treatment with a relatively acceptable toxicity profile, despite the fact that two patients developed pulmonary tuberculosis. After the third year of therapy, 59% of patients continued to be treated with infliximab. The concomitant use of methotrexate was associated with the continuation of infliximab therapy.