The antihyperglycemic drug metformin and the thrombocyte aggregation inhibitor dipyridamole are often used concomitantly in patients with diabetes who have suffered a transient ischemic attack or stroke. It has recently been suggested that the gastrointestinal absorption of metformin is mediated by the equilibrative nucleoside transporter 4 (hENT4). Dipyridamole has been reported to inhibit hENT4 transport in vitro. The aim of this research proposal is to study the pharmacokinetic interaction between metformin and dipyridamole. The investigators hypothesize that dipyridamole reduces the gastrointestinal absorption of metformin. If this hypothesis can be confirmed, then the results of this study can explain in part the high variability in plasma metformin concentrations in patients treated with diabetes, and can be used to optimize pharmacotherapy in patients with diabetes.

Inclusion Criteria:

• Age 18-50 years
• Written informed consent

Exclusion Criteria:

• Smoking
• Hypertension (systolic blood pressure > 140 mmHg and/or diastolic blood pressure > 90 mmHg)
• Diabetes Mellitus (fasting glucose >7.0 mmol/L or random glucose >11 mmol/L)
• History of any cardiovascular disease
• Concomitant use of medication
• Renal dysfunction (MDRD <60 ml/min)
• ECG abnormalities, other than firs grade AV-block or right bundle branch block