Clonidine effect on insulin secretion and lipolysis in man

Effect of clonidine on blood glucose levels in euglycemic and alloxan-induced diabetic rats and its interaction with glibenclamide

Objectives:

Clonidine, a known antihypertensive, is currently used for many purposes including diabetic gastroparesis, postmenopausal hot flushes, opioid/nicotine/alcohol withdrawal. Its effects on carbohydrate metabolism appear to be variable. Hence, the present study was undertaken to evaluate the influence of clonidine on euglycemic and alloxan -induced diabetic rats and its interaction with glibenclamide.

Materials and Methods:

Alloxan - induced (150 mg/kg, i.p) diabetic rats were divided into six groups of six animals each. Group I - Normal Control; Group II - Nondiabetic + Clonidine (25 μg/kg); Group III - Diabetic Control; Group IV - Diabetic + Glibenclamide (5 mg/kg); Group V - Diabetic + Glibenclamide + Clonidine. All drugs were given orally once daily. Blood glucose was estimated from rat tail vein using glucometer before start of the experiment and at the end of 30 days.

Results:

After 30 days of treatment, clonidine (25 μg/kg) produced significant hyperglycemia in both euglycemic and diabetic rats. It also reduced the hypoglycemic effect of glibenclamide in diabetic rats.

Conclusion:

The results of present study indicate that clonidine has hyperglycemic effect and it also interacts with glibenclamide to reduce its hypoglycemic activity. If these findings are true to human beings then clonidine should not be used in diabetic patients on sulfonylureas.

Beta-blockers and glucose control

Literature on the effects of beta-blockers on blood glucose is reviewed. Data are presented regarding the adrenergic influences on glucose regulation and the effects of beta-blockade during hypo- and hyperglycemia in normal and diabetic individuals. beta-adrenergic stimulation enhances insulin and glucagon secretion, as well as glycogenolysis, gluconeogenesis, and lipolysis. alpha-adrenergic stimulation inhibits insulin secretion and may inhibit glucagon secretion and enhance liver glycogenolysis. In nondiabetics, beta-blockers represent minimal risk of affecting glucose control. In insulin-dependent diabetics, beta-blockers can prolong, enhance, or alter the symptoms of hypoglycemia, while hyperglycemia appears to be the major risk in noninsulin-dependent diabetics. beta-blockers can potentially increase blood glucose concentrations and antagonize the action of oral hypoglycemic drugs.

Clonidine and glucose intolerance

Changes in carbohydrate metabolism were observed in a diabetic, hypertensive patient managed with clonidine. After a slight increase in the clonidine dose, his blood sugar control deteriorated. However, when the clonidine was withdrawn, the glucose intolerance subsided. Because clonidine preferentially binds alpha 2-subtype receptors, we investigated animal pancreatic tissue by radioligand binding technique and found it to contain alpha-adrenergic receptors predominantly of the alpha 2-subtype. In consideration of the response from withdrawal of clonidine and the results of our radioligand studies, wer concluded the glucose intolerance seen in this patient was most likely due to the specific action of clonidine on alpha 2-pancreatic receptors.

Oral glucose tolerance and insulin response after one week's clonidine treatment in hypertensive patients

Acute clonidine administration is known to induce a significant rise in plasma glucose in man. In order to evaluate the possible effect of prolonged drug treatment on glucose metabolism, paired OGTTs were performed in 12 hypertensive patients (6 with normal and 6 with abnormal glucose tolerance) in basal conditions and following 1-week's administration of clonidine (0.15 mg every 8 h) Basal plasma glucose and serum insulin concentration as well as glucose tolerance and insulin response to oral glucose did not change in either group after treatment. Although the mechanism(s) mediating the transient hyperglycemic action of clonidine are not fully understood, the present findings indicate that this drug does not exert diabetogenic effects during chronic treatment, and suggest that homeostatic mechanisms may counteract the acute effect of clonidine on glucose metabolism.