Optimal vial sizes for infliximab injection: a simulation study of Japanese demographic data

Drug wastage costs in the medical field must be reduced, particularly for expensive biological drugs. In Japan, the Ministry of Health, Labour and Welfare (MHLW) has developed specific criteria for the divided use of injectable vials and vial sharing of anticancer injection drugs to reduce drug wastage. This study investigates the optimal vial size for infliximab infusion to reduce drug wastage in Japan.

A log-normal distribution was assumed for body weight, and hypothetical data were simulated using the software R. We assumed the average wastage in milligrams (mg) by considering different vial sizes in addition to the existing 100 mg size. We also assumed 18 different vial size combinations for rheumatism patients by gender. The range was 10-95 mg with 5 mg increments. Using the total amount of wasted doses for the existing 100 mg size as a baseline, we evaluated the effect of using additional vial sizes on the total amount of wasted doses.

The average cost of infliximab wastage per case was found to be US$ 353.8 for males and US$ 359.6 for females. For a 15 mg plus 100 mg combination, the average cost of infliximab wastage per case became US$ 20.2 for males and US$ 26.1 for females. In other words, infliximab wastage would be reduced by 94.3% for males and 92.8% for females.

Adding a 15 mg vial size to the existing 100 mg size can reduce wastage. Producing drugs in different vial sizes can thus help significantly reduce the cost burden on the national health care system.