Beta blockers such as atenolol, carvidolol and metoprolol are commonly used drugs in the treatment of high blood pressure and heart disease. These medications decrease sympathetic nervous system stimulation thereby lowering the blood pressure and reducing the morbidity and mortality of cardiovascular disease. The use of beta blockers can have side effects on glucose metabolism.
What are Beta Blockers
Beta blockers are often the first medications used in the treatment of high blood pressure, after heart attacks and in the treatment of chest pain. Beta blockers block the body's beta 1 and 2 receptor sites. When adrenaline is released by the sympathetic nervous system, it affects the beta receptors. When they are blocked, adrenaline cannot stimulate those receptor sites. The heart does not increase its rate or raise blood pressure in response to the adrenaline.
Beta1 and Beta2 Receptors
The body has two beta receptors, 1 and 2. Beta1 receptors are directly responsible for heart rate and the strength of the heart beat. Beta2 receptors control your smooth muscles, muscles that you don't have actual motor control over such as those muscles that constrict blood vessels. Most beta blockers block both 1 and 2, but some of them are more selective and block mostly beta1 receptors while only blocking beta 2 receptors a little.
Hypoglycemia
The blockade of beta2 receptors in the body by beta blockers can induce hypoglycemia or low blood sugar. Beta2 receptors normally induce glucose production by stimulating breakdown of glucose stores in the liver and delivering that glucose to the system. When this process is blocked, low blood sugar may occur. When the body glucose gets too low, it normally stimulates the sympathetic nervous system to increase the heart rate as a signal that glucose needs to be replenished. Your palms may get sweaty and you might also feel a little shaky. This response is blocked with the use of beta-blockers and hypoglycemia may go unnoticed until it is too late. This is particularly problematic in diabetics.
Hyperglycemia
In a 2010 research article published in "Current Medical Research and Opinion," hyperglycemia or high blood glucose was noted to occur in patients taking non-vasodilating beta blockers, or nonselective beta blockers such as atenolol and metoprolol. These beta blockers were associated with worsening glucose and cholesterol control. In contrast, vasodilating beta blockers or selective beta blockers such as caredilol, labetalol and nebivolol had a more favorable effect on glucose and cholesterol control.
