Several classes of drugs are used to treat hypertension.
Diuretics help the kidneys get rid of excess salt and water. Thiazide diuretics are the mainstays of anti-hypertensive therapy and are usually the first type of drug selected for most people with hypertension. Thiazide diuretics are especially helpful for treating older people (over age 60) and African-Americans. (African-Americans are more likely to be salt-sensitive, so they respond well to these drugs.) Diuretics are often used in combination with other antihypertensive drugs.
There is strong evidence that diuretics work just as well as newer drugs in lowering blood pressure and are more effective in preventing heart failure, heart attack, and stroke.
The 3 main types of diuretics include:
Thiazide diuretics. These include chlorthalidone (Thalitone, Clorpres), chlorothiazide (Diuril), indapamide (Lozol), hydrochlorothiazide (HydroDIURIL), bendroflumethiazide (Naturetin), methyclothiazide, (Enduron), and metolazone (Zaroxolyn). All of these prescription drugs are available in generic form. In most cases, thiazides are preferred to other diuretics for treatment of high blood pressure. Chlorthalidone is often the brand prescribed.
Potassium-sparing diuretics. These include amiloride (Midamor, generic), spironolactone (Aldactone, generic), and triamterene (Dyrenium, generic).
Loop diuretics. Because loop diuretics act faster than other diuretics it is important to avoid dehydration and potassium loss. Loop diuretics include bumetanide (Bumex, generic), furosemide (Lasix, generic), ethacrynic acid (Edecrin, generic), and torsemide (Demadex, generic).
Common diuretic side effect symptoms include:
- Frequent urination
- Increased thirst
- Muscle cramps or weakness
Thiazide and loop diuretics reduce the body's supply of potassium (hypokalemia), which, if left untreated, increases the risk for arrhythmias. Arrhythmias are heart rhythm disturbances that can lead to cardiac arrest, although they rarely do. If you experience reduced potassium, your doctor will prescribe a lower dose of your current diuretic, recommend potassium supplements, or switch to a potassium-sparing diuretic either alone or in combination with a thiazide.
Potassium-sparing drugs have their own risks, which include dangerously high levels of potassium in people with existing elevated levels of potassium or in those with damaged kidneys. However, all diuretics are generally more beneficial than harmful.
Other health concerns associated with thiazide diuretics include:
- Thiazide diuretics may raise blood sugar levels and increase the risk for developing type 2 diabetes.
- Erectile dysfunction (impotence) can be an uncommon side effect of thiazides.
- Elevated uric acid levels, and possibly gout.
Angiotensin-converting enzyme inhibitors (ACEIs) widen blood vessels and decrease the workload of the heart. They treat high blood pressure and can also help protect the heart and kidneys.
An ACE inhibitor may be used as an initial blood pressure medication for non-black patients younger than age 60 years. ACEIs are also often used in combination with other anti-hypertensive medications.
Brands. ACE inhibitors include captopril (Capoten, generic), enalapril (Vasotec, generic), quinapril (Accupril, generic), benazepril (Lotensin, generic), ramipril (Altace, generic), perindopril (Aceon, generic), and lisinopril (Prinivil, Zestril, generic).
Common side effect symptoms of ACE inhibitors include:
- Low blood pressure is the main side effect of ACE inhibitors. This can be severe in some people, especially at the start of therapy.
- An irritating cough is a common side effect, which some people find intolerable.
- ACE inhibitors can harm a developing fetus and should not be used during pregnancy. Women who become pregnant should change from ACE inhibitors to another type of blood pressure drug as soon as possible. Women of child-bearing age who are considering becoming pregnant should also discuss other medications with their doctors.
- ACE inhibitors can increase potassium levels, particularly in people with kidney disease.
Uncommon Side Effects of ACE Inhibitors.
- ACE inhibitors protect against kidney disease, but they may also increase potassium retention by the kidneys. If potassium levels become extremely high (hyperkalemia), they can cause the heart to stop beating (cardiac arrest). This side effect is uncommon, except in people with significant kidney disease. Because of this risk, ACE inhibitors are not usually used in combination with potassium-sparing diuretics or potassium supplements.
- A rare but severe side effect is granulocytopenia, an extreme reduction in infection-fighting white blood cells.
- In very rare cases, people suffer a sudden and severe allergic reaction, called angioedema that causes swelling in the eyes and mouth and may close off the throat.
People who have difficulty tolerating ACE inhibitor side effects are usually switched to an angiotensin-receptor blocker (ARB).
Angiotensin-Receptor Blockers (ARBs)
ARBs, also known as angiotensin II receptor antagonists, are similar to ACE inhibitors in their ability to widen blood vessels and lower blood pressure. They may have fewer or less-severe side effects than ACE inhibitors, especially coughing, and are sometimes prescribed as an alternative to ACE inhibitors. In general they are prescribed to people who cannot tolerate or did not respond to ACE inhibitors.
Brands. Losartan (Cozaar, Hyzaar, generic), olmesartan (Benicar) candesartan (Atacand), telmisartan (Micardis), eprosartan (Teveten), irbesartan (Avapro), valsartan (Diovan), and azilsartan (Edarbi).
A combination medication containing candesartan and the diuretic hydrochlorothiazide (Diovan HCT, Atacand HCT) is also available. Exforge HCT is a triple-combination medication that combines in one pill valsartan along with the calcium-channel blocker amlodipine and the diuretic hydrochlorothiazide. Tribenzor combines in one pill olmesartan, amlodipine, and hydrochlorothiazide.
Side Effects. Common side effects of ARBs may include:
- Low blood pressure
- Dizziness and lightheadedness
- Raised potassium levels
- Nasal congestion
NOTE: ARBs should not be used during pregnancy.
Calcium-Channel Blockers (CCBs)
Calcium-channel blockers (CCBs), also known as calcium antagonists, help relax blood vessels. Along with thiazide diuretics, CCBs appear to work better than other drug classes for lowering blood pressure in African-Americans.
Brands. Diltiazem (Cardizem, Dilacor), amlodipine (Norvasc), felodipine (Plendil), isradipine (DynaCirc), verapamil (Calan, Isoptin, Verelan), nisoldipine (Sular), nicardipine (Cardene), and nifedipine (Adalat, Procardia).
All these prescription medications are available as generics. For people who have both high blood pressure and high cholesterol, Caduet combines in one pill amlodipine and the statin drug atorvastatin.
Side Effects. Side effects of CCBs may include:
- Swelling in the feet
- Erectile dysfunction
- Food interactions (Do not take CCBs with grapefruit or Seville orange products.)
Beta Blockers. Beta blockers help slow your heart rate and lower blood pressure. They are usually prescribed for people who have hypertension and coronary artery disease or heart failure. Brands include acebutolol (Sectral, generic), metoprolol (Lopressor, generic), and carvedilol (Coreg, generic). These drugs can have serious side effects and must be used carefully. Most important, suddenly stopping a beta blocker drug can potentially cause a heart attack. Your doctor will need to slowly decrease your dose before you can stop taking this medication.
Alpha Blockers. Alpha blockers such as doxazosin (Cardura, generic), prazosin (Minipress, generic), and terazosin (Hytrin, generic) help widen small blood vessels. They are generally not used as first-line drugs for high blood pressure, but are prescribed if other drugs do not work or as add-on medication.
Vasodilators. Vasodilators help open blood vessels by relaxing muscles in the blood vessel walls. These drugs are usually used in combination with a diuretic or a beta blocker. They are rarely used by themselves. Brands include hydralazine (Apresoline, generic), clonidine (Catapres, generic), and Minoxidil (Loniten, generic). Some of these drugs should be used with caution or not at all in people who have angina or who have had a heart attack.
Aliskiren (Tekturna). Aliskiren (Tekturna, Amturnide) is a new kind of antihypertensive drug called a direct renin inhibitor. It blocks renin, a kidney enzyme associated with high blood pressure. Aliskiren is also available in the 2-in-1 combination pills Tekturna HCT (aliskiren and the diuretic hydrochlorothiazide) and Tekamlo (aliskiren and the calcium channel blocker amlodipine). Aliskiren is prescribed either alone or in combination with other blood pressure medications. However, people with diabetes or kidney impairment should not take aliskiren along with ACE inhibitors or ARBs because of increased risk for kidney damage and other problems. Aliskiren should not be used during pregnancy as it can cause injury or death to the fetus.