The impact of biosimilar insulin introduction on insulin utilization in a tertiary public hospital in Malaysia: an interrupted time series analysis

Diabetes mellitus imposes a substantial clinical and economic burden on health systems, with insulin therapy essential for achieving and maintaining glycaemic control in many patients. Biosimilar insulin offers opportunities to improve access and manage costs in healthcare settings, but evidence on real-world utilization responses remains limited. This study evaluated the impact of biosimilar isophane insulin and biphasic isophane insulin introduction on insulin utilization in a tertiary public hospital in Malaysia. An interrupted time series analysis using autoregressive integrated moving average (ARIMA) modeling was conducted on dispensing data from January 2013 to February 2020. Biosimilar introduction in February 2017 was assessed using level and slope change parameters. Biosimilar introduction was associated with significant increases in utilization for insulin types. For isophane insulin, utilization increased by 24% (β = 0.213, P = 0.002), followed by a modest decline over time (β = −0.007, P = 0.010). For biphasic isophane insulin, an immediate increase of 97% was observed (β = 0.677, P = 0.005), with no significant post-intervention trend change (P = 0.702). Biosimilar insulin introduction led to uptake but variable sustainability across insulin types. Optimizing biosimilar adoption is essential for improving access to insulin and strengthening diabetes management within health systems.