Growth of diabetes drug expenditure decomposed-A nationwide analysis

The aim of this study was to quantify different factors underlying the growth of diabetes drug expenditure in Finland.

Data representing purchases of antidiabetic agents between 2003 and 2015 were extracted from a nationwide prescription register. By using Fisher's Ideal Indexes, the per capita expenditure growth for both insulins and non-insulin antidiabetic agents was decomposed into six different determinants: purchase volume, purchase size, switches between therapeutic classes, switches within therapeutic classes, unit costs and switches to generic alternatives.

Between 2003 and 2015, the per capita expenditure on insulins increased by €8.64 and on non-insulins by €13.73. For insulins, holding other factors constant, change in the number of purchases represented a €4.67 increase in expenditure, change in the size of purchases a €4.33 increase and switches between therapeutic classes a €4.07 increase. For non-insulins, change in the number of purchases represented a €10.22 increase in expenditure and switches between therapeutic classes, a €10.17 increase. Changes in purchase size increased the non-insulin per capita expenditure by €1.48. For both insulins and non-insulins, changes in prices and product level switches had decreasing effects on expenditures.

The main drivers of the growth in diabetes drug expenditure were volume growth and switches to newer and more expensive drugs. Price changes, however, had a decreasing effect on the overall diabetes drug expenditure.