April 15, 2012
The first beta-blocker drug approved by the FDA in 1967 was developed by Sir James Black, an accomplishment for which he was awarded the Nobel Prize in Medicine in 1988 (Stapleton, 1997). Sir Black took a different approach to the treatment of angina pectoris—instead of using drugs to increase the amount of oxygen delivered to the heart, Black sought to find a drug that could reduce the amount of oxygen required by the heart.
The drugs in this classification are subdivided into two categories: non-selective and selective (cardioselective). Major drugs in the non-selective beta-blocker category include carteolol, nadolol, ...view middle of the document...
Hypertension is characterized by blood pressure over 120/80mm Hg (Turley, 2010). Both non-selective and cardioselective beta-blockers decrease heart rate and contractility, and dilate the blood vessels, thereby decreasing blood pressure. Cardioselective beta-blockers are prescribed to asthmatic patients to avoid the effects of bronchioconstriction due to blockage of beta2 receptors in the lungs. Beta-blockers’ effect of slowing heart rate and contractility is also used to treat both tachycardia4 and atrial flutter and fibrillation5. When heart rate is decreased, so is the amount of oxygen required by the heart. Decreasing the amount of oxygen required by the heart decreases the pain of angina pectoris6. Therefore, the beta-blockers atenolol, metoprolol, nadolol, and propranolol are prescribed to reduce the pain associated with angina pectoris. Reduction of heart rate and vasodilation help to relieve the strain on the heart, and therefore beta-blockers are prescribed to treat hypertrophic subaortic stenosis7, congestive heart failure8 and to prevent myocardial infarction9. Though their mechanism of action is poorly understood in the prevention of migraine headaches, five beta-blockers are commonly prescribed: atenolol, metoprolol, nadolol, propranolol, and timolol. When applied to the eyes, beta blockers decrease the intraocular pressure associated with glaucoma10 by decreasing the production of aqueous humor11.
Patients with the above mentioned heart problems and/or hypertension should experience a decrease in blood pressure, along with a decrease in heart rate and contractility when treated with beta-blockers. These effects lead to an overall decrease in morbidity and mortality in these patients (Butler et al, 2006). Studies have shown that treatment with beta-blockers, along with behavioral management is effective in the prevention of recurring migraine headaches (Holroyd et al, 2010). When treated with beta-blockers, patients with glaucoma should experience a decrease in intraocular pressure, which will relieve pressure on the optic nerve, thereby preventing the loss of vision. Treatment with beta-blockers cannot reverse any loss of vision already experienced, but can help to prevent further loss of vision.
Beta-blockers are most commonly administered orally (available in tablet, capsule, and solution forms), and can also be administered intravenously. When treating glaucoma, beta-blockers are applied topically to the eyes in the form of drops.
Side effects may include dizziness, light-headedness, blurred vision, and drowsiness. A chilled feeling may occur, especially at the extremities, due to reduced circulation. Known adverse effects include congestive heart failure, bronchospasm, and bradyarrythmias12.
Patients should not abruptly discontinue use of beta-blockers, as it could cause life-threatening hypertension or arrhythmias. In addition to following medication instructions, patients are given instructions for weight loss, diet...