Propranolol is contraindicated in diabetes mellitus due to:

(Masks the hypoglycemic symptoms): Ref: 127-KDT, 478-BB (139-KDT6th)HYPOGLYCEAMIA: - especially with non selective (Propranolol) members, which block b2 receptors, and especially in Diabetes and after substantial exercise, due to impairment of the normal sympathetic mediated homeostatic mechanism for maintaining the blood glucose ie recovery from iatrogenic hypoglycaemia is delayed but since a-adrenoceptors are not blocked, hypertension (which may be severe) can occur as the sympathetic system discharges in an 'attempt' to reverse the hypoglycemia, In addition, the symptoms of hypoglycaemia in so for as they are mediated by the sympathetic (anxiety, palpitations) will not occur (through cholinergic sweating will) and the patients may miss the warning symptoms of hypoglycaemia and slip into coma b1 - selective drugs are preferred in diabetes.* b- blockade leads to decreased glycogenolysis and decreased glucogon secretion. Therefore if a Type I DM is to be given propranolol very careful monitoring of blood glucose is essential, because pronounced hypoglycemia may ocular after insulin injection, b-blocker also atemuate the normal physiologic response to hypoglycemia (87-Lippincott's 4th)