What medications are available for high blood pressure?
Aggressive drug treatment of long-term high blood pressure can significantly reduce the incidence of mental decline and death from heart disease and other serious physical effects of hypertension. In people with diabetes, controlling both blood pressure and blood glucose levels prevents serious complications of that disease. Anti-hypertensive agents may even prevent mental decline, including in people genetically susceptible to Alzheimer's disease. There are many types of medications used to treat high blood pressure. Angiotensin-converting enzyme inhibitors, or ACE inhibitors, block the production of a body chemical that constricts the arteries. ACE inhibitors include benazepril hydrochloride, enalapril maleate, and quinapril hydrochloride. Angiotensin II receptor blockers block the effect of a body chemical that constricts the arteries. This group of medications includes valsartan, losartin potassium, and candesartan.
Beta-blockers lower the heart rate and increase the amount of blood pumped with each heartbeat. Common beta-blockers include atenolol, propanolol hydrochloride, and nadolol. Calcium channel blockers lower the heart rate and relax the blood vessels. Some common calcium channel blockers include amlodipine besylate, diltiazem hydrochloride, nifedipine, and verapamil. Diuretics, or water pills, help the body get rid of extra fluid and sodium. Common diuretics include furosemide, hydrochlorothiazide, and chlorthalidone. . Sympathetic nerve inhibitors keep the nervous system from constricting arteries. This group includes clonidine hydrochloride, guanabenz acetate, and alpha methyldopa. Vasodilators relax the muscles in the blood vessel walls and allow the vessels to dilate. Common vasodilators include isosorbide dinitrate and hydralazine.
Water pills (diuretics)
Diuretics are used very widely to control mildly high blood pressure. They increase urine output, decrease blood volume, and dilate the arteries. These actions lower blood pressure. Usually diuretics are given in combination with other classes of blood pressure medications. Diuretics are among the oldest known medications for treating hypertension. They work in the tiny tubes (tubules) of the kidneys to remove salt from the body. Diuretics may be used as single drug treatment (monotherapy) for hypertension. More frequently, however, low doses of diuretics are used in combination with other anti-hypertensive medications to enhance the effect of the other medications.
The diuretic hydrochlorothiazide (Hydrodiuril) works in the far end (distal) part of the kidney tubules. In a low dose of 12.5 to 25 mg per day, this diuretic may improve the blood pressure-lowering effects of other anti-hypertensive drugs. The idea is to treat the hypertension without causing the adverse effects that are sometimes seen with the higher doses of hydrochlorthiazide. These side effects include potassium depletion and elevated levels of triglyceride (fat), uric acid, and glucose (sugar).
Occasionally, when salt retention causing swelling (edema) is a major problem, the more potent loop diuretics may be used in combination with other anti-hypertensive medications. (The loop diuretics are so called because they work in the loop segment of the kidney tubules to eliminate salt.) The most commonly used diuretics to treat hypertension include hydrochlorthiazide, the loop diuretics, furosemide (Lasix) and torsemide (Demadex), the combination of triampterene and hydrochlorothiazide (Dyazide), and metolazone (Zaroxolyn). Note that diuretics probably should not be used in pregnant women.
Beta-blockers reduce heart rate and decrease the force of heart contraction, thereby reducing the pressure generated by the heart. They are preferred in people who have associated coronary heart disease, angina, or recent heart attack. Beta-blockers include Propranolol (Inderal), metoprolol (Lopressor), atenolol (Tenormin).
The sympathetic nervous system is a part of the nervous system that helps to regulate certain involuntary (autonomic) functions in the body, including those of the heart and blood vessels. As part of that system, beta-receptors (receivers that respond to stimuli) in the heart increase the heart rate and the strength of heart contractions (pumping action). Beta-blockers acting on the heart, therefore, slow the heart rate and reduce the force of cardiac contraction. Meanwhile, beta-receptors in the smooth muscle of the peripheral arteries in tissues throughout the body and in the smooth muscle of the lung airways serve to relax these muscles.
Accordingly, beta-blockers cause contraction of the smooth muscle of the peripheral arteries and thereby decrease the blood flow to the tissues throughout the body. As a result, the patient may experience, for example, coolness in the hands and feet. Likewise, in response to the beta-blockers, the airways are squeezed (constricted) by the contracting smooth muscle. This squeezing (impingement) on the airway causes wheezing, especially in individuals with a tendency for asthma. In short, beta-blockers reduce both the force of the heart's pumping action and the blood pressure that the heart generates in the arteries.
Beta-blockers remain useful medications in treating hypertension, especially in patients with a fast heartbeat while resting (tachycardia), cardiac chest pain (angina), or a recent heart attack (myocardial infarction). For example, beta-blockers appear to improve long-term survival when given to patients who have had an acute heart attack. Whether beta-blockers can prevent heart problems (are cardio-protective) in patients with hypertension any more than other anti-hypertensive medications, however, is uncertain. Beta-blockers do seem to help treat chronic anxiety or migraine headaches in people with hypertension. The common side effects of these drugs include depression, fatigue, nightmares, sexual impotence in males, and increased wheezing in people with asthma. The beta-blockers include atenolol (Tenormin), propranolol (Inderal), and metoprolol (Toprol).
Calcium channel blockers
Calcium-channel blockers reduce muscle tension in the arteries, expanding them and creating more room for the blood flow. In addition, they slightly relax the heart muscle so it beats more slowly, reducing blood pressure. Calcium channel blocking agents work by relaxing the muscle in the walls of the arteries. They also reduce the force of contraction of the heart. Calcium channel blocking agents include Nifedipine (Procardia), diltiazem (Cardizem), verapamil (Isoptin, Calan), nicardipine (Cardene), amlodipine (Norvasc), felodipine (Plendil). Calcium channel blockers inhibit the movement of calcium into the muscle cells of the heart and arteries. The calcium is needed for these muscles to contract. These drugs, therefore, lower blood pressure by decreasing the force of the heart's pumping action (cardiac contraction) and relaxing the muscle walls of the arteries. Three major types of calcium channel blockers are used. One type is the dihydropyridines, which do not slow the heart rate or cause other abnormal heart rates or rhythms (cardiac arrhythmias). These drugs include amlodipine (Norvasc), sustained release nifedipine (Procardia XL, Adalate CC), felodipine (Plendil), and nisoldipine (Sular).
The other two types of calcium channel blockers are referred to as the non-dihydropyridine agents. One type is verapamil (Calan SR) and the other is diltiazem (Cardizem, Tiazac, Dilacor). Both the dihydropyridines and the non-dihydropyridines are very useful when used alone or in combination with other anti-hypertensive agents. The non-dihydropyridines, however, are not recommended (contraindicated) in congestive heart failure or with certain arrhythmias. Sometimes, however, these same dihydropyridines are useful in preventing certain other arrhythmias.
Many of the calcium channel blockers come in a short-acting form and a long-acting (sustained release) form. The short-acting forms of the calcium channel blockers, however, may have adverse long-term consequences, such as strokes or heart attacks. These effects are presumably due to the wide fluctuations in the blood pressure and heart rate that occur during treatment. The fluctuations result from the rapid onset and short duration of the short-acting compounds. When the calcium channel blockers are used in sustained release preparations, however, less fluctuation occurs. Accordingly, the sustained release forms of calcium channel blockers are probably safe for long-term use. The main side effects of these drugs include constipation, swelling (edema), and a slow heart rate (only with the non-dihydropyridine types).
Angiotensin-converting enzyme (ACE) inhibitors and ACE receptor blockers (ARBs)
ACE inhibitors stop the production or block the action of a chemical called angiotensin II, a very potent chemical that causes blood vessels to contract, a cause of high blood pressure. Blockage of this chemical causes the blood vessels to relax. ACE inhibitors include Captopril (Capoten), enalapril (Vasotec), lisinopril (Zestril, Prinivil), quinapril (Accupril), fosinopril (Monopril). ARBs include losartan (Cozaar), candesartan (Atacand), valsartan (Diovan), irbesartan (Avapro), olmesartan (Benicar). Side effects are infrequent but sometimes they can worsen kidney function. ACE inhibitors sometimes cause dry cough. ARBs usually have fewer side effects.
Alpha-blockers relax blood vessels by blocking messages from the nervous system that cause muscular contraction. Alpha-blockers lower blood pressure by blocking alpha-receptors in the smooth muscle of peripheral arteries throughout the tissues of the body. The alpha-receptors are part of the sympathetic nervous system, as are the beta-receptors. The alpha-receptors, however, serve to narrow (constrict) the peripheral arteries. Accordingly, the alpha-blockers cause the peripheral arteries to widen (dilate) and thereby lower the blood pressure.
Recent evidence, however, suggests that using alpha-blockers alone as a first line drug choice for hypertension may actually increase the risk of heart-related problems, such as heart attacks or strokes. Alpha-blockers, therefore, should not be used as an initial drug choice for the treatment of high blood pressure. Examples of alpha-blockers include terazosin (Hytrin) and doxazosin (Cardura).
Alpha-blockers are particularly useful in patients with enlargement of the prostate gland (which usually occurs in older men) because these drugs reduce the problems associated with urinating. Alpha-blockers alone, however, have a relatively small blood pressure-lowering effect. Accordingly, when hypertension coexists with prostatic enlargement, another anti-hypertensive medication should be used together with an alpha-blocker. For example, tamsulosin (Flomax) is an alpha-blocker that works well in combination with other anti-hypertensive medications. Such a combination can relieve urinating problems without causing an excessive decrease in the blood pressure.
Blockers of central sympathetic (autonomic nervous) system
These agents block messages from the autonomic nervous system that contract blood vessels. The autonomic nervous system is the part of the nervous system that is automatic and controls heart rate, breathing rate, and other basic functions. Their effect is to relax blood vessels, thus lowering blood pressure.