Reduction of the acute bioavailability of metformin by the α‐glucosidase inhibitor acarbose in normal man

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Abstract
In a double‐blind cross‐over study, we investigated a possible influence of the α‐glucosidase inhibitor acarbose on the bioavailability of the biguanide compound metformin. Each of the six healthy young male volunteers was randomly allocated during two consecutive 7 day periods to either acarbose (days 1–3: 3 times 50mg day−1; days 4–7: 3 times 100 mg day−1) or placebo. At day 7 and 14 of the study, the overnight‐fasted subjects ingested 1000mg metformin with the first bite of a standardized breakfast (500kcal; 60 g carbohydrates) and together with either placebo or 100 mg acarbose. Acarbose significantly (P < 0·05) reduced the meal‐induced increase in blood glucose and plasma insulin levels. Acarbose induced a significant (P < 0·05) reduction in early (90, 120, 180min) serum levels, peak concentrations (Cmax: 1·22 ± 0·14 vs. 1·87 ± 0·60 mgl−1) and area under the curve of metformin (AUC 0–540min: 423±55 vs. 652±55 mg minl−1), but did not diminish its 24 h urinary excretion. In conclusion, acarbose significantly reduces the acute bioavailability of metformin in normal subjects.