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High Blood Pressure Medication - Diuretics

Diuretics are sometimes called "water pills." They work by helping your kidneys flush excess water and salt from your body. This reduces the amount of fluid in your blood, and your blood pressure goes down.

Diuretics also relax the arteries. There are different types of diuretics. They are often used along with other high blood pressure medicines and may be combined with another medicine in one pill.

The dose of these medicines will be different for different patients. Follow your doctor's orders or the directions on the label. The dosing information shown includes only the average doses of these medicines. If your dose is different, do not change it unless your doctor tells you to do so.

Overview. Thiazide or thiazide-like diuretics are commonly used to treat high blood pressure (hypertension). High blood pressure adds to the workload of the heart and arteries. If it continues for a long time, the heart and arteries may not function properly. This can damage the blood vessels of the brain, heart, and kidneys, resulting in a stroke, heart failure, or kidney failure. High blood pressure may also increase the risk of heart attacks. These problems may be less likely to occur if blood pressure is controlled.

Thiazide diuretics are also used to help reduce the amount of water in the body by increasing the flow of urine. They may also be used for other conditions as determined by your doctor. Thiazide diuretics are available only with your doctor's prescription.

Thiazide-type diuretics have been the basis of antihypertensive therapy in most outcome trials. In these trials, including the recently published Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), diuretics have been virtually unsurpassed in preventing the cardiovascular complications of hypertension. The exception is the Second Australian National Blood Pressure trial which reported slightly better outcomes in White men with a regimen that began with an ACEI compared to one starting with a diuretic. Diuretics enhance the antihypertensive efficacy of multi-drug regimens, can be useful in achieving BP control, and are more affordable than other antihypertensive agents. Despite these findings, diuretics remain underutilized.

Thiazide-type diuretics should be used as initial therapy for most patients with hypertension, either alone or in combination with one of the other classes (ACEIs, ARBs, BBs, CCBs) demonstrated to be beneficial in randomized controlled outcome trials. If a drug is not tolerated or is contraindicated, then one of the other classes proven to reduce cardiovascular events should be used instead.

Thiazide diuretics

Chlorothiazide (Diuril)



Chlorthalidone (Generic)



Hydrochlorothiazide (Microzide, Hydrodiuril†)



Polythiazide (Renese)



Indapamide (Lozol†)



Metolazone (Mykrox)



Metolazone (Zaroxolyn)



Loop diuretics

Bumetanide (Bumex†)



Furosemide (Lasix†)



Torsemide (Demadex†)



Potassium-sparing diuretics

Amiloride (Midamor†)



Triamterene (Dyrenium)



Before Using This Medicine. In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For thiazide diuretics, the following should be considered:

  • Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to sulfonamides (sulfa drugs), bumetanide, furosemide, acetazolamide, dichlorphenamide, methazolamide, or to any of the thiazide diuretics. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.
  • Pregnancy—When this medicine is used during pregnancy, it may cause side effects including jaundice, blood problems, and low potassium in the newborn infant. In addition, although this medicine has not been shown to cause birth defects or other problems in animals, studies have not been done in humans. In general, diuretics are not useful for normal swelling of feet and hands that occurs during pregnancy. They should not be taken during pregnancy unless recommended by your doctor.
  • Breast-feeding—Thiazide diuretics pass into breast milk. These medicines also may decrease the flow of breast milk. Therefore, you should avoid use of thiazide diuretics during the first month of breast-feeding.
  • Children—Although there is no specific information comparing the use of thiazide diuretics in children with use in other age groups, these medicines are not expected to cause different side effects or problems in children than they do in adults. However, extra caution may be necessary in infants with jaundice, because these medicines can make the condition worse.
  • Older adults—Dizziness or lightheadedness and signs of too much potassium loss may be more likely to occur in the elderly, who are more sensitive than younger adults to the effects of thiazide diuretics.
  • Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking thiazide diuretics, it is especially important that your health care professional know if you are taking any of the following:
    • Cholestyramine or
    • Colestipol—Use with thiazide diuretics may prevent the diuretic from working properly; take the diuretic at least 1 hour before or 4 hours after cholestyramine or colestipol
    • Digitalis glycosides (heart medicine)—Use with thiazide diuretics may cause high blood levels of digoxin, which may increase the chance of side effects
    • Lithium (e.g., Lithane)—Use with thiazide diuretics may cause high blood levels of lithium, which may increase the chance of side effect
  • Other medical problems—The presence of other medical problems may affect the use of thiazide diuretics. Make sure you tell your doctor if you have any other medical problems, especially:
    • Diabetes mellitus (sugar diabetes)—Thiazide diuretics may increase the amount of sugar in the blood
    • Gout (history of) or
    • Lupus erythematosus (history of) or
    • Pancreatitis (inflammation of the pancreas)—Thiazide diuretics may make these conditions worse
    • Heart or blood vessel disease—Thiazide diuretics may cause high cholesterol levels or high triglyceride levels
    • Liver disease or
    • Kidney disease (severe)—Higher blood levels of the thiazide diuretic may occur, which may prevent the thiazide diuretic from working properly

Proper Use of This Medicine. This medicine may cause you to have an unusual feeling of tiredness when you begin to take it. You may also notice an increase in the amount of urine or in your frequency of urination. After you have taken the medicine for a while, these effects should lessen. In general, to keep the increase in urine from affecting your sleep:

  • If you are to take a single dose a day, take it in the morning after breakfast.
  • If you are to take more than one dose a day, take the last dose no later than 6 p.m., unless otherwise directed by your doctor.

However, it is best to plan your dose or doses according to a schedule that will least affect your personal activities and sleep. Ask your health care professional to help you plan the best time to take this medicine.

Take each dose at the same time each day. This medicine works best if there is a constant amount in the blood.

For patients taking this medicine for high blood pressure:

  • In addition to the use of the medicine your doctor has prescribed, appropriate treatment for your high blood pressure may include weight control and care in the types of foods you eat, especially foods high in sodium. Your doctor will tell you which factors are most important for you. You should check with your doctor before changing your diet.
  • Many patients who have high blood pressure will not notice any signs of the problem. In fact, many may feel normal. It is very important that you take your medicine exactly as directed and that you keep your appointments with your doctor even if you feel well.
  • Remember that this medicine will not cure your high blood pressure but it does help control it. Therefore, you must continue to take it as directed if you expect to lower your blood pressure and keep it down. You may have to take high blood pressure medicine for the rest of your life . If high blood pressure is not treated, it can cause serious problems such as heart failure, blood vessel disease, stroke, or kidney disease.

For patients taking the oral liquid form of hydrochlorothiazide, which comes in a dropper bottle:

  • This medicine is to be taken by mouth. The amount you should take is to be measured only with the specially marked dropper.

Precautions While Using This Medicine. It is important that your doctor check your progress at regular visits to make sure that this medicine is working properly.

This medicine may cause a loss of potassium from your body. To help prevent this, your doctor may want you to:

  • eat or drink foods that have a high potassium content (for example, orange or other citrus fruit juices), or
  • take a potassium supplement, or
  • take another medicine to help prevent the loss of the potassium in the first place.

It is very important to follow these directions. Also, it is important not to change your diet on your own. This is more important if you are already on a special diet (as for diabetes), or if you are taking a potassium supplement or a medicine to reduce potassium loss. Extra potassium may not be necessary and, in some cases, too much potassium could be harmful.

Check with your doctor if you become sick and have severe or continuing vomiting or diarrhea. These problems may cause you to lose additional water and potassium.

For patients taking this medicine for high blood pressure

  • Do not take other medicines unless they have been discussed with your doctor. This especially includes over-the-counter (nonprescription) medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems, since they may tend to increase your blood pressure.

For diabetic patients:

  • Thiazide diuretics may raise blood sugar levels. While you are using this medicine, be especially careful in testing for sugar in your blood or urine.

Thiazide diuretics may cause your skin to be more sensitive to sunlight than it is normally. Exposure to sunlight, even for brief periods of time, may cause a skin rash, itching, redness or other discoloration of the skin, or a severe sunburn. When you begin taking this medicine:

  • Stay out of direct sunlight, especially between the hours of 10:00 a.m. and 3:00 p.m., if possible.
  • Wear protective clothing, including a hat. Also, wear sunglasses.
  • Apply a sun block product that has a skin protection factor (SPF) of at least 15. Some patients may require a product with a higher SPF number, especially if they have a fair complexion. If you have any questions about this, check with your health care professional.
  • Apply a sun block lipstick that has an SPF of at least 15 to protect your lips.
  • Do not use a sunlamp or tanning bed or booth.

If you have a severe reaction from the sun, check with your doctor.

Side Effects of This Medicine. Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • Rare – Black, tarry stools;  blood in urine or stools;  cough or hoarseness;  fever or chills;  joint pain;  lower back or side pain;  painful or difficult urination ;  pinpoint red spots on skin;  skin rash or hives;  stomach pain (severe) with nausea and vomiting;  unusual bleeding or bruising;  yellow eyes or skin 
  • Signs and symptoms of too much potassium loss – Dryness of mouth;  increased thirst;  irregular heartbeat;  mood or mental changes;  muscle cramps or pain;  nausea or vomiting;  unusual tiredness or weakness ;  weak pulse 
  • Signs and symptoms of too much sodium loss – Confusion;  convulsions;  decreased mental activity;  irritability ;  muscle cramps;  unusual tiredness or weakness 

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

  • Decreased sexual ability;  diarrhea;  dizziness or lightheadedness when getting up from a lying or sitting position;  increased sensitivity of skin to sunlight;  loss of appetite;  upset stomach 

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

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