The effects of cholinergic blockade on the plasma glucose and insulin responses during oral and intravenous glucose administration were studied. Propantheline (30 mg.) was given by mouth 45 minutes before standard glucose tolerance testing to produce symptomatic cholinergic blockade. In 10 normal subjects a flattening of the over-all plasma glucose response to oral glucose was observed compared with the control test, whereas insulin secretion was not different. In seven patients with repeated episodes of symptomatic reactive hypoglycemia, cholinergic blockade eliminated both symptomatic and chemical hypoglycemia in each, raising the mean nadir glucose from 44 ± 4 mg./dl. to 84 ± 8 mg./dl. (p<0.01) and significantly reducing insulin secretion. In contrast, following intravenous glucose challenge, cholinergic blockade produced no significant difference in the rate of glucose utilization or insulin secretion in either group.
These results are compatible with the hypothesis that excessive vagal stimulation may contribute to the hypoglycemia seen in patients with reactive hypoglycemia but suggest that the predominant effect is on the gastrointestinal tract rather than on pancreatic islets directly. These studies confirm that anticholinergic drugs may be useful adjuvants in treating these patients.