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P319. Dose variations with adalimumab and infliximab in the treatment of Crohn's disease: A Canadian assessment

J. Lachaine1, C. Beauchemin1, A. Goyette2, M. Martel2

1University of Montreal, Montreal, QC, Canada; 2Abbott Laboratories, Saint-Laurent, QC, Canada

Aim: In Canada, adalimumab and infliximab are approved for the treatment of moderate to severe active Crohn's disease (CD) when response to conventional therapy is inadequate. The recommended maintenance dose is 40 mg every other week for adalimumab and 5 mg/kg every 8 weeks for infliximab. In case of incomplete response, product monographs suggest that the dose may be increased to 40 mg per week for adalimumab and up to 10 mg/kg every 8 weeks for infliximab. Dose increases have an impact on treatment cost, but the extent to which higher doses are used has yet to be described. The objective of this study was to analyze, in a real world setting, dose variations among Canadian CD patients who initiated an adalimumab or infliximab treatment.

Methods: A retrospective cohort study was conducted using data from the Regie de l'assurance maladie du Quebec (RAMQ) for a random sample of patients with a diagnosis of CD, who had initiated adalimumab or infliximab between February 2008 and December 2008. Patients had to be continuously covered by the RAMQ, from 12 months before and 12 months after initiation of adalimumab or infliximab. For adalimumab, dose increase was considered when the dose received exceeded 40 mg every other week over at least an 8-week period. For infliximab, dose increase was considered either when the dose was increased or interval between doses was reduced during two periods of 8 weeks after the third injection.

Results: The cohort included a total of 289 patients. During the study period, 134 with infliximab and 155 patients were initiated with adalimumab from which 47 had previously used infliximab. The mean age of the study population was 42.2 years (SD=16.9) and a higher proportion of subjects were females (62.6%). Average treatment duration was 240 days with both treatments. After 12 months, 13.5% (21/155) of patients with adalimumab and 22.4% (30/134) of patients with infliximab had experienced a dose increase (p < 0.05). For the subgroup of adalimumab patients naïve to infliximab and those who had previously used infliximab, dose escalation occurred in 12.0% and 17.0% respectively. Average medications cost in the year following initiation of adalimumab or infliximab, for patients who did not increase dose or reduced interval between doses were CAD10,250 and CAD14,868 respectively (p < 0.01). For patients who experienced a dose increase or reduced interval between doses, average medications cost was CAD19,789 with adalimumab and CAD25,550 with infliximab (p = 0.013).

Conclusion: CD patients treated with infliximab had a significantly higher rate of dose increases compared with patients treated with adalimumab. Results of this RAMQ database analysis illustrate that, in a real-world setting, dose increase or reduction of interval between doses are associated with increased treatment costs. In both recommended and adjusted dosing, adalimumab demonstrated significant cost savings over infliximab.