The effects of thiopurines on white cell count are well documented.
We compared the effects of infliximab 5 mg/kg monotherapy and combination of infliximab with thiopurines on the total and differential white cell count (WBC).
13 IBD patients treated with infliximab monotherapy and 18 IBD patients treated with a combination of infliximab and thiopurines were included in the study. Using retrospective data, cell counts were examined prior to induction of infliximab, and at 6 weeks and 1 year post-induction.
The patients on combination therapy had an absolute WBC at 52 weeks of 5.7 whereas that of patients on Infliximab monotherapy at the same time point was 8.3 with comparable neutrophil count of 3.4 and 5.4. The results showed a significant reduction in white cell count and neutrophils at 6 weeks which persisted at 52 weeks in both groups (p < 0.05) with a greater drop in patients on combination infliximab and thiopurine (p < 0.05) as compared to Infliximab monotherapy. There was no significant change in the lymphocyte count.
Full blood counts should be closely monitored in all patients starting infliximab therapy, in particular patients receiving concomitant thiopurines.