Data from international observational studies show that a considerable proportion of patients use higher dosages of infliximab (INF) than the usual 3 mg every 8 weeks used in Germany for treatment of rheumatoid arthritis. The Data are, however, inconsistent and vary between countries. Using data from the German Biologics Register RABBIT we investigated: (1) how dosage of INF develops during the first year of treatment in routine care, and (2) how dosage translates into clinical effectiveness.
We analysed data from 344 patients who started a treatment with INF at their inclusion into the register and who were observed for the subsequent 12 months. Mean dosage at 3 months (after the loading dose) was 3.2 mg/kg body weight/infusion and 3.3 mg/kg after 1 year. If we also consider shortening the infusion intervals, the mean dosages at the start and after 1 year were 4.0 mg/kg body weight every 8 weeks.
Patients who were treated with low dosages of up to 3 mg/kg/8 weeks showed significantly less improvement (EULAR response) than those who were treated with higher dosages.
The data show that German rheumatologists are aware of the high costs of treatment and try to use the lowest possible dosage. However, for a certain proportion of the patients this might be insufficient.