Benefits associated with a broad selection of dosage strengths for recombinant factor VIII products

Factor VIII (FVIII) concentrates for haemophilia A patients are dosed according to body weight. This results in a continuous range of prescribed doses, which challenges pharmacies to find dosage strengths closest to the prescribed dose while utilizing the least number of vials. This study was conducted to determine whether a broader selection of FVIII dosage strengths results in improved dispensing accuracy and an increased number of single-vial users. This research retrospectively analyzed a US pharmacy database of prescriptions filled in 2008. Recombinant FVIII (rFVIII) therapies were classified by the range of dosage strengths offered in 2008: Group 1 had three dosage strengths; Group 2 had four dosage strengths; and Group 3 had six dosage strengths. A total of 76,584 dispensed doses of rFVIII for 1,244 patients were included in this analysis. Dispensing accuracy (calculated as both the absolute and relative difference between dispensed and prescribed dose) was significantly better for Group 3 (23.2 IU, 1.2%) than Groups 1 (33.5 IU, 1.6%) and 2 (50.2 IU, 2.4%) (both P < 0.01). In addition, the average number of unique actual rFVIII potencies dispensed per month was highly correlated (-0.977) with dispensing accuracy for each dosage strength group. Among Groups 1, 2 and 3, 23.0%, 44.9% and 73.4% of patients, respectively, had at least one single vial option dispensed (P < 0.0001). A broader selection of rFVIII dosage strengths and more actual rFVIII potencies were associated with improved dispensing accuracy and more single-vial users. This may translate into less waste, cost savings, increased convenience and improved adherence to physician-prescribed regimens.