Trends in use and costs of prescription medication in patients with type 1 diabetes: 9-year follow-up after kidney transplantation

Aims: We estimated long-term trends in prescription medication utilization and costs in patients with type 1 diabetes in two different transplant cohorts (Group 1: transplantation 1986-1999, n = 180; Group 2: transplantation 2000-2008, n = 150). Methods: Data obtained from the Finnish Diabetic Nephropathy Study were linked with the Drug Prescription Register (purchases of medications 1995-2009). Generalized linear mixed models under gamma distribution were used to evaluate the medication costs. Results: The total costs of medication decreased (Group 1 from €11,290 to €8760; Group 2 from €12,800 to €9790) during the follow-up (P < 0.0001). The same trend was observed for immunosuppressive drug costs (P < 0.0001). Although the cost profiles were similar for the groups (P = 0.9), the cost level in Group 2 was higher than in Group 1 (P < 0.0001). In Group 1 the most common immunosuppressive combination was cyclosporine, azathioprine and corticosteroid, while cyclosporine, mycophenolate mofetil (MMF) with/without corticosteroid was the most common in Group 2. The estimated average costs of cyclosporine in combination with MMF were 84% (€4130) higher than with azathioprine. Conclusions: Since diabetes or other drugs had only marginal impact on the total costs, the decreasing trend was mainly due to the costs of immunosuppressants. This finding is consistent with the recent guidelines which recommend reducing doses of immunosuppressants over time to minimize sideeffects. The cost levels differed depending on the combinations of immunosuppressive drugs in use. Those who had MMF in the regimen generated higher costs.