Hyperglycemic action of 2-(2,6-dichlorphenylamino)-2-imidazoline hydrochloride in relation to its hypertensive effect

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.

Dual action of clonidine on insulin release: suppression, but stimulation when alpha 2-adrenoceptors are blocked

As shown previously clonidine reduces glucose-stimulated insulin release and this effect is mediated by inhibitory postsynaptic alpha 2-adrenoceptors. The present experiments demonstrate that clonidine has the additional property to also stimulate insulin release. This became evident when the alpha 2-adrenoceptors of isolated islets were blocked by benextramine, and thus protected from being stimulated by clonidine. In the presence of benextramine, clonidine no longer reduced, but on the contrary enhanced, the release of insulin in response to glucose. In control experiments benextramine by itself failed to affect insulin release from isolated islets. These results show that the imidazoline derivative clonidine shares the property of other imidazoline compounds to enhance the insulin response to glucose. All of these agents may stimulate insulin by binding to "imidazoline-preferring" sites, that clearly differ from alpha-adrenoceptors.

Nephrotic-range proteinuria and hyperglycemia associated with clonidine therapy

Glycosuria, hyperglycemia, and nephrotic-range proteinuria developed in a 68-year-old patient after clonidine was added to a stable antihypertensive regimen, which included metoprolol, of three years' duration. He later became glucose-intolerant with fasting hyperglycemia. Clonidine has been reported to transiently impair glucose tolerance. Persistent diabetes in a previously normoglycemic patient following clonidine has not been reported, and it supports the possibility that clonidine and metoprolol may have additive effects in suppressing endogenous insulin secretion.

The effect of clonidine injected centrally on serum-free fatty acids and glucose concentration in the rat

Clonidine administered intracerebroventricularly (ICV) to conscious rats induced a significant dose-dependent increase in serum free fatty acid (FFA) and blood glucose levels. The rise in FFA and glucose concentrations after a dose of 10 micrograms averaged 80%-100% of the control levels. The alpha-adrenoceptor antagonists yohimbine, phentolamine, and phenoxybenzamine, administered alone ICV, did not substantially influence the control FFA and glucose levels. A hyperlipemic response to clonidine (10 micrograms) was abolished by an ICV pretreatment with yohimbine and was strongly antagonized by phentolamine but not by phenoxybenzamine. The clonidine-induced hyperglycemia was significantly diminished by phentolamine and only partly by yohimbine, whereas phenoxybenzamine was ineffective here. The histamine H2-receptor antagonist cimetidine, given ICV, failed to change these effects of clonidine. It seems likely that clonidine, given ICV, induces hyperlipemic and hyperglycemic effects through the stimulation of central alpha-adrenoceptors but not histamine H2-receptors. The lipolytic action of the drug depends more on the activation of alpha 2-adrenoceptors.