Effects of selective and non-selective beta-blockers on the alanine and free fatty acid responses to glucagon challenge in hemodialysis patients.

Hypoglycemia is frequently reported in hemodialysis patients on propranolol. The effects of beta-blockers on the glucose, alanine and free fatty acid responses to glucagon challenge (2 mg) in fourteen hemodialysis patients were studied. Patients on propranolol had impaired glycemic response while those on metoprolol had decreased response only before dialysis. There was a significant negative correlation between propranolol level (log-transformed) and glycemic responses, suggesting that propranolol has direct effect on the latter. Hemodialysis patients had fasting alanine levels comparable to those of normal subjects. After glucagon challenge, the decrements in alanine level had no consistent relationship to the impaired glycemic response. Thus suppression of gluconeogenesis is unlikely to be the prime cause of propranolol-induced hypoglycemia. The basal free fatty acid levels were significantly lower among hemodialysis patients on propranolol. This limited availability of free fatty acid as well as the inhibitory effect on hepatic glucagon-stimulated glucose output may contribute to the predisposition to hypoglycemia in dialysis patients given propranolol. The results suggest that metoprolol has less interference on energy substrate supply in hemodialysis patients under fasting conditions.