Background: Few studies have evaluated drug utilisation to improve sustainability in Gestational Diabetes Mellitus (GDM) management. ADIPS guidelines only require these women to receive medication from week 24 gestation to delivery. The Australian Pharmaceutical Benefits Scheme (PBS) permits prescribers to write a subsidised insulin isophane human 100 units/mL prescription (Protophane InnoLet®, 25 devices) for $31.60 (concession $7.70) rather than $140.62 (cost to government for the maximum quantity). We evaluated a quality improvement strategy to determine utility and feasibility of staged dispensing to reduce isophane insulin wastage at Mater Mothers’ Hospital, Brisbane.
Method: We conducted a prospective study of consenting antenatal women diagnosed with GDM and prescribed isophane insulin (Protaphane®), 30/5/2025-3/6/2024. Initial part-supply was dispensed, with remaining devices stored under cold chain. Residual devices could be collected if further insulin was required, avoiding further costs. Dispensing records determined actual insulin usage.
Results: For the 222 audited women, 337 insulin devices were dispensed as the primary supply, with 11 of these women receiving 20 devices as secondary supply. The 758 surplus devices (versus 1,115 allowable under PBS) equated to a total saving of $31,358.26.
Conclusions: Our results strongly indicate that the current practice of supplying 5x5 Innolet devices of isophane insulin (current PBS maximum supply) is a gross patient oversupply. Supplying patients with sufficient insulin for their needs, from their current gestation to term, would greatly reduce the cost burden to the PBS, with a saving of $7,613,074, based on the Australian Institute of Health and Welfare 2024 predicted data for 2025.1