Infliximab utilization patterns within an alternate site of care setting among patients with Inflammatory Bowel Disease

Abstract

To examine infliximab dosing patterns among patients with inflammatory bowel disease (IBD) receiving therapy in an alternate site-of-care setting (i.e., ambulatory infusion centers). A retrospective analysis of drug utilization data from nine ambulatory infusion centers (AIC) was conducted. Patients were required to be aged ≥18, have ≥ 2 ICD-9 codes for Crohn's disease (555.x) or ulcerative colitis (556.x), and have ≥3 infusions administered at an AIC during the measurement period (6/2008 - 3/2010). Both “new’ patients (those receiving their first infliximab dose within the AIC) and “existing” patients (those receiving infliximab doses at another site prior to the AIC) were included in the analysis. Available data included demographic information, diagnosis fields, and infliximab infusion information. Patient weight was also available, allowing for direct calculation of infliximab dose. Dosing intervals were calculated as the number of days between infusions. Mean and median infusion intervals and infliximab doses were compared to FDA prescribing information. To measure possible interval and dose changes over time, repeated-measures analyses of covariance (ANCOVA) were conducted. A total of 167 patients with IBD were included in the analysis (Crohn's disease=107, ulcerative colitis=60). Of these patients, 84 were new patients and 83 were existing patients. Approximately 56% of the new patients were male, mean age was 45 years, mean weight was 82 kg, and mean number of infusions during the measurement period was seven. Among existing patients, 45% were male, mean age was 40 years, mean weight was 74 kg, and mean number of infusions during the study period was eight. Approximately 94% of new patients (n = 79/84) received a starting infliximab dose of 5mg/kg. Over the first eight infusions, the mean infliximab dose for new patients ranged from 4.94 mg/kg to 5.18 mg/kg. Among existing patients, the mean infliximab dose ranged from 5.52 mg/kg to 5.77 mg/kg over the first eight infusions received within the AIC setting. Among new patients, the median number of days between the 1st and 2nd infusion was 14 days, and between the 2nd and 3rd infusion was 28 days. For the third through eighth infusions, the median number of days between infusions ranged from 55 to 56 days. Similarly, among existing patients, the median number of days between the first eight infusions ranged from 50 to 56 days. Based on ANCOVA results, there was no evidence of systematic change in dose or dosing interval over time. Among IBD patients receiving infusions in an AIC, the infliximab dose and dosing frequency were consistent with FDA prescribing information and there was no evidence of systematic dose or dosing frequency change over time. Infliximab utilization patterns within the AIC setting, as identified in this analysis, appear to be consistent with the in-office infusion setting1. Evaluation of other factors, such as patients' preferences, may be useful in further characterizing this site of care and supporting optimal site-of-care decision-making.