Improvement of Glucose Tolerance by Verapamil in Patients with Non‐Insulin‐Dependent Diabetes Mellitus

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Abstract
To study the effect of verapamil on the glucose tolerance and insulin response to oral glucose, 6 healthy subjects and 15 patients with non-insulin-dependent diabetes mellitus (NIDDM) were investigated. In the healthy individuals, 3 tests were performed on separate days: a standardized oral glucose load, an identical glucose load during i.v. infusion of verapamil, and a 3rd oral glucose load after 1 wk of oral verapamil treatment. No significant differences were found when the insulin and glucose responses with and without verapamil were compared. The patients with NIDDM were divided into 3 groups. Two tests were performed on separate days in each patient: group 1, a standardized oral glucose load and an identical glucose load during i.v. verapamil infusion; group 2, a standardized oral glucose load and a similar glucose load after 1 wk of oral verapamil treatment; group 3, the protocol of group 2 was followed but oral placebo was given instead of verapamil. In groups 1 and 2, verapamil improved the tolerance for oral glucose; the insulin response remained unaffected. In group 3, no significant differences were found in the insulin and glucose responses to the 2 oral glucose loads. Verapamil apparently improves the tolerance for oral glucose regardless of the route of administration in patients with NIDDM. This may be accomplished by an effect of verapamil on glucose regulatory factors other than insulin.