Contraindicated metformin prescriptions in German type 2 diabetics: Data from a general population based study. Is metformin therapy carried out critically enough?

Context: Studies report prevalences of contraindications to metformin use in patients with type 2 diabetes (T2D) to be between 19 – 94%. This reflects international evidence in general. The picture for Germany lacks reliable information, especially based on routinely collected data.

Aim: The aim of this study is to analyze the current metformin treatment practice for patients with T2D in Germany, particularly with regard to metformin prescriptions in patients having contraindications.

Methods: We conducted a cross-sectional study to analyze how often physicians prescribe metformin for patients with T2D (n = 102821) especially in those having contraindications to its use. Contraindications to metformin therapy were limited to chronic renal impairment, chronic liver disease, cardiac failure and chronic alcoholism and were identified by the ICD-10 WHO GM codes. The analysis based on the research database of the “Gesundheitsforen Leipzig” consisting of German health insurance claims data from 2006 to 2011.

Results: Antidiabetic medication was prescribed for 81040 (78.8%) patients with T2D. Among them, 48480 (59.8%) had enchased prescriptions for metformin. 1456 (3.0%) metformin user had a contraindication. However, non-metformin user had significantly more contraindications to metformin (6.6%) than metformin user (3.0%, p < 0.001). In total, 5023 (4.9%, n = 102821) patients with T2D had contraindications to metformin use. Type of contraindications and clinical outcomes are presented.

Conclusion: Contraindicated metformin prescriptions in Germany are not as high as in other studies. Thus, metformin therapy is carried out quite reasonably. However, further research is needed to analyze the reasons for a metformin prescription despite of contraindications.