Antidiabetic therapy in real practice: indicators for adherence and treatment cost

Giorgio L Colombo,^1,2 Elisa Rossi,⁴ Marisa De Rosa,⁴ Danilo Benedetto,³ Antonio V Gaddi<sup>3

1</sup>School of Pharmacy, Department of Drug Sciences, University of Pavia, Pavia, ²S.A.V.E. Studi Analisi Valutazioni Economiche, Milan, ³CINECA – Bologna; ⁴Centro Aterosclerosi GC Descovich, Dipartimento di Medicina Interna e dell'Invecchiamento, University of Bologna, Bologna, Italy

Background: Type 2 diabetes has become a disease with a high economic and social impact. The ARNO Observatory is a clinical data warehouse consisting of a network of local health care units (ASL) scattered throughout the Italian territory which collects data on health care consumption for about 10.5 million people. The purpose of this study was to evaluate the use of antidiabetic drugs with particular reference to type of treatment. The analyses were carried out on a sample of 169,375 patients treated with oral blood glucose-lowering drugs in 2008 from a total population of 4,040,624 health care beneficiaries at 12 local health care units in the ARNO Observatory.
Methods: Patients were considered “on treatment with oral blood glucose-lowering drugs” if they had received at least one prescription of an antidiabetic drug (Anatomical Therapeutic Chemical code A10B) during 2008. The patients were divided into three treatment groups, ie, monotherapy, fixed-combination drugs, and dual therapy. The following indicators were assessed: number of patients treated with an oral antidiabetic drug, mean number of hospitalizations, mean number of specialist examinations, and mean expenditure per treated patient. Adherence was assessed using the medication possession ratio indicator (MPR).
Results: Patients treated with oral blood glucose-lowering drugs comprised 4.2% of the investigated population, and had an average age of 68.9 years. The mean annual number of hospitalizations was lower in the dual therapy group (298 versus 328 per 1000 patients in the sample), while the average number of specialist examinations was lower in the fixed-combination group (30.1 versus 35.1). Patients on monotherapy showed a better percentage of adherence for glimepiride (70.5%) and pioglitazone (70.4%), whereas the best adherence in the fixed-combination therapy group was recorded for metformin + pioglitazone (75.5%). The average annual cost per diabetic patient was €2388, with differences between the monotherapy (€2321), fixed-combination (€2270), and dual therapy (€2465) groups. Fixed combination therapy involved a lower mean expenditure for insulin, other drugs, and specialist and diagnostic care. Thiazolidinediones (such as pioglitazone) showed the lowest average annual cost per patient among the monotherapies, with a marked decrease in costs for hospitalization, specialist care, and diagnostics.
Conclusion: The results of our study should be extended to other regional/national reference local health care units in order to define and compare average standard costs per pathology throughout the wide sample considered in this research work. Appropriate drug prescribing is of critical importance in order to achieve therapeutic objectives and to optimize the use of resources in modern health care systems.

Keywords: type 2 diabetes, oral antidiabetic drugs, pharmacoeconomics, health care costs, adherence, medication possession ratio