Blood pressure is influenced by how much water is in your body and salt intake. Diuretics reduce water and sodium in your body, and for decades have been the chief method for treating high blood pressure. They are still considered the first choice by many experts, especially for treating the elderly and African American patients.
Diuretics come in many brands and are generally inexpensive. Some need to be taken once a day, others twice a day. There are three primary types:
Thiazides -- thiazides block sodium absorption from the kidney back into the blood. They are either taken alone for mild to moderate high blood pressure or used in combination with other types of drugs. There are many thiazides and thiazide-containing drugs. Some common ones are chlorothiazide (Diuril), chlorthalidone (Hygroton), indapamide (Lozol), and hydrochlorothiazide (Esidrix, HydroDiuril).
Loop diuretics -- loop diuretics block sodium absorption from the kidney back into the blood. They tend to act faster than thiazides and have a great diuretic effect. It is important, therefore, to control the medication to avoid dehydration and excessive loss of potassium. Loop diuretics include bumetanide (Bumex), furosemide (Lasix), and ethacrynic acid (Edecrin).
Potassium-sparing agents -- these block the action of aldosterone, so that more potassium is left in the blood, and more sodium and water are excreted in the urine. some potassium-sparing diuretics include amiloride (Midamor), spironolactone (Aldactone), and triamterene (Dyrenium).
Problems with diuretics
The loop and thiazide diuretics deplete the body's supply of potassium, which, if left untreated, increases the risk for arrhythmias. Arrhythmias are heart rhythm disturbances that can, in rare instances, lead to cardiac arrest. If potassium levels are lowered, physicians will either prescribe lower doses of the current diuretic, recommend potassium supplements, and/or use potassium-sparing diuretics.
Potassium-sparing drugs have their own risks, which include raising potassium to dangerously high levels, particularly in people who started out with somewhat high potassium or those with damaged kidneys.
Common side effects
Common side effects of diuretics are:
Fatigue, muscle cramps, or weakness from low potassium levels
Loss of sexual drive (from potassium-sparing diuretics)
Hair growth, menstrual changes, and deepening voice in women (from potassium-sparing diuretics)
Breast swelling in men; breast tenderness in women (from potassium-sparing diuretics)
Allergic reactions -- if you are allergic to sulfa drugs, you should not use thiazides either
Diuretics can trigger attacks of gout. Potassium-sparing diuretics may increase the risk of bleeding in the stomach or intestines. Thiazide diuretics may raise cholesterol level or blood sugar -- therefore, these levels should be followed closely in people with high cholesterol or diabetes. Loop diuretics may also raise blood sugar.
Arrhythmias (abnormal heart rhythms) can occur because of changes in potassium levels in the blood, especially when the diuretic is taken with other medications (such as digoxin). Nonsteroidal anti-inflammatory drugs (like ibuprofen) may interfere with diuretics.
Review Date: June 3, 2003
Reviewed By: Jacqueline A. Hart, M.D., Department of Internal Medicine,
Newton-Wellesley Hospital, Harvard University and Senior Medical Editor,
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