Source: http://www.emedicinehealth.com/high_blood_pressure/page9_em.htm

Medications most often prescribed for high blood pressure include the following:
Water pills (diuretics)

• Diuretics are used very widely to control mildly high blood pressure, and are often used in combination with other medications.
• They increase sodium excretion and urine output and decrease blood volume. The sensitivity to the effect of other hormones in your body is decreased.
• Example - Hydrochlorothiazide (HydroDIURIL)

Beta-blockers

• Beta-blockers reduce heart rate and decrease the force of heart contraction, thereby reducing the pressure generated by the heart.
• They are preferred for people who have associated coronary heart disease, angina, or history of a heart attack, since they also prevent recurrent heart attacks and sudden death.
• Examples - Carvedilol (Coreg), metoprolol (Lopressor), atenolol (Tenormin)
• Side effects - Fatigue, depression, impotence, nightmares

Calcium channel blockers

• 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.
• Examples - Nifedipine (Procardia), diltiazem (Cardizem), verapamil (Isoptin, Calan), nicardipine (Cardene), amlodipine (Norvasc), felodipine (Plendil)
• Side effects - Ankle swelling, fatigue, headache, constipation, flushing

Angiotensin-converting enzyme (ACE) inhibitors

• ACE inhibitors stop the production 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.
• Examples - Captopril (Capoten), enalapril (Vasotec), lisinopril (Zestril, Prinivil), quinapril (Accupril), fosinopril (Monopril)
• Side effects are infrequent but sometimes they can worsen kidney function and raise blood potassium levels, especially in patients with damaged kidneys. ACE inhibitors sometimes cause dry cough and rarely angioedema (severe swelling around the trachea/windpipe).

Angiotensin receptor blockers or ARBs

• ARBs work on receptors in tissues all over the body to prevent uptake of angiotensin II, and therefore inhibit the vasoconstrictor effect of angiotensin II.
• Examples - Losartan (Cozaar), valsartan (Diovan), candesartan (Atacand), and irbesartan (Avapro)
• Side effects tend to be less with ARBs than ACEIs with much less cough.

Alpha-blockers

• Alpha-blockers relax blood vessels by blocking messages from the nervous system that cause muscular contraction.
• Examples - Terazosin (Hytrin), doxazosin (Cardura)
• Since publication of a study known as the ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) in 42,000 patients, and premature termination of the alpha-blocker arm (discontinuation of treatment in the group receiving alpha-blockers) because of excessive incidence of congestive heart failure, alpha-blockers are no longer frequently prescribed and are primarily used in men with associated prostatism (benign prostatic hyperplasia, or enlargement of the prostate) symptoms.

Blockers of central sympathetic (autonomic nervous) system

• These agents block messages out of the brain 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.
• The effect of these drugs is to relax blood vessels, thus lowering blood pressure. These agents are not as popular because of excessive side effects, and no randomized trials demonstrate their effectiveness in lowering heart attacks, strokes, etc.
• Example - Clonidine (Catapres)

Direct vasodilators

• Direct vasodilators relax (dilate) the blood vessels to allow blood to flow under lower pressure.
• These medications are often given through an IV line in an emergency (that is, in malignant hypertension).
• Examples - Nitroprusside (Nitropress), diazoxide (Hyperstat). Oral medications are hydralazine and minoxidil.

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