How you take a drug affects how well it works and how safe it will be for you. Sometimes it can be as important as what you take. Timing, what you eat and when you eat, proper dose, and many other factors can mean the difference between getting better, staying the same, or even getting worse. This drug information page is intended to help you make your treatment work as well as possible. It is important to note, however, that this is only a guideline. You should talk to your doctor or pharmacist about how and when to take any prescribed drug.

This installment in a series of articles on commonly prescribed drugs is about a particular group of diuretics called potassium-sparing diuretics-hydrochlorothiazide combinations. They are used primarily for treating high blood pressure.

This medicine is a combination of two types of diuretics--potassium-sparing and hydrochlorothiazides--that help decrease the amount of water and sodium in the body by acting on the kidneys to increase the flow of urine. Other diuretics tend to reduce the amount of potassium in the body. But potassium sparing diuretics help retain or spare this electrolyte. Potassium is vital to body functions, including muscle contraction.

These drugs come in pill form in three formulations: amiloride and hydrochlorothiazide; spironolactone and hydrochlorothiazide; and triamterene and hydrochlorothiazide, the most frequently prescribed. See accompanying list for brand names.

Conditions These Drugs Treat

Potassium-sparing diuretics-hydrochlorothiazide combinations are most commonly used to control high blood pressure (hypertension). Untreated, high blood pressure can cause serious problems such as heart failure, blood vessel disease, stroke, or kidney failure.

People taking this medicine for high blood pressure may have to take it the rest of their lives, even though they may not feel sick.

In addition to the drug, doctors may also prescribe a low-salt diet to help reduce hypertension. The medicine is usually more effective when the diet is followed properly.

This medicine is also used to reduce swelling, such as in the ankles or lungs, caused by an excessive amount of water in the body. However it is usually not used for treating the normal swelling of feet and hands that occurs during pregnancy.

How to Take

Because this medicine may increase the frequency of urination, it is best to plan your dose or doses so they least affect your daily schedule or sleep. If you are taking only one dose a day, take it in the morning after breakfast. If you are taking more than one dose, take the last dose no later than 6 p.m., unless directed otherwise by your doctor. To make it easier to remember to take your medicine, take it at the same time each day.

If the medicine upsets your stomach, it may be taken with meals or a glass of milk. This will help prevent stomach upset.

Missed Doses

A missed dose should be taken as soon as possible. However, if it's almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take double doses.

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Relief of Symptoms

If this medicine is being used to control hypertension, there may be no noticeable effects. High blood pressure may not have any outward signs. In fact, most people with high blood pressure feel normal.

It is important to continue to take the medicine exactly as directed and to keep appointments with your doctor even if you feel well.

If this medicine is being used to reduce swelling, its effects should be noticeable in anywhere from a few days to a few weeks, depending on the condition it is being used to treat.

Side Effects and Risks

Initially, this medicine may cause unusual tiredness and an increase in the amount of urine and frequency of urination. These effects should lessen after you have taken the medicine for a few weeks.

This medicine also may increase or decrease the amount of potassium in your body, depending on which of the two components of the drug have the predominant effect. For this reason, doctors ordinarily do blood tests the first few months you're on the drug and periodically thereafter to monitor the amount of potassium in your body. To offset any decrease or increase, your doctor may instruct you to eat or avoid certain foods. For example, you may be advised to eat foods or drink beverages that have a high potassium content (e.g., citrus fruit juices and bananas), use salt substitutes, or take a potassium supplement. However, do not use salt substitutes or low-sodium milk unless your doctor tells you to because they may contain potassium. Too much or too little potassium can be harmful.

The symptoms of an increase in potassium are dry mouth, increased thirst, irregular heartbeat, mood or mental changes, muscle cramps or pain, shortness of breath or difficulty breathing, unusual tiredness or weakness, a weak pulse, and numbness or tingling in hands, feet or lips. If any of these occurs, check with your doctor as soon as possible.

If you are already on a special diet, as for diabetes, tell your doctor. Hydrochlorothiazide can raise your blood sugar.

This medicine also may cause increased sensitivity to sunlight in a few people. Exposure to sunlight, even for brief periods, may cause severe sunburn, skin rash, redness, itching, discoloration of skin, or change in vision. If you notice an increased sensitivity to sunlight while taking this medicine, it's wise to take precautions to reduce your exposure to direct sunlight. If you have a severe reaction from the sun, discuss it with your doctor.

If a pregnant woman takes hydrochlorothiazide, there is a slight chance her newborn infant may have low potassium. For this reason, it is usually not prescribed during pregnancy. The drug has not been shown to cause birth defects.

Rarely, these diuretics may cause a number of other side effects. Check with your doctor as soon as possible if you have any of the following:

  • black, tarry stools
  • blood in urine or stools
  • cough or hoarseness
  • fever or chills
  • joint pain
  • lower back pain, side pain, or joint pain
  • painful or difficult urination
  • pinpoint-size red spots on skin
  • skin rash or hives
  • severe stomach pain with nausea and vomiting
  • unusual bleeding or bruising
  • yellow eyes or skin

In addition, on rare occasions triamterene may cause a bright red tongue, a burning feeling in the tongue, and cracked corners of the mouth. Check with your doctor as soon as possible if these occur.

As your body adjusts to this medicine, other side effects may occur, but they usually do not require medical attention unless they continue or are bothersome. The most common are loss of appetite, nausea and vomiting, stomach cramps and diarrhea, and upset stomach. Less common are decreased sexual ability, dizziness or lightheadedness when getting up from lying down or sitting, and headache.

Spironolactone sometimes causes breast tenderness in women, enlarged breasts in men, clumsiness, deepening of voice in females, increased hair growth in females, irregular menstrual periods, and sweating. These conditions gradually disappear over two or three months after the medicine is stopped.

Amiloride sometimes causes constipation.

Other rarer side effects not listed here may occur in a few people. If you have any new symptoms while taking this medication, check with your doctor.

Before Using This Medicine

Tell your doctor:

  • if you have ever had any unusual or allergic reaction to amiloride, spironolactone, triamterene, sulfonamides, bumetanide, furosemide, acetazolamide, dichlorphenamide, methazolamide, hydrochlorothiazide, or any of the other thiazide diuretics
  • if you are on a special diet, such as low-sodium. This could affect how the drug works in your body.
  • if you are allergic to any substance, such as foods, sulfites or other preservatives, or dyes. These diuretics, like most other medicine that comes in pill form, contain preservatives and dyes that may cause an allergic reaction in some people.
  • if you are pregnant or may become pregnant. In general, diuretics should not be taken during pregnancy unless recommended by the doctor.
  • if you are breast-feeding. Although spironolactone, triamterene and hydrochlorothiazide may pass into breast milk, they have not been shown to cause problems in nursing babies. It is not known whether amiloride passes into breast milk.
  • if you have any of the following medical problems: sugar diabetes, kidney disease, liver disease, menstrual problems or breast enlargement, inflammation of the pancreas, or a history of gout, kidney stones, or lupus erythematosus.

Precautions and Warnings

If you get sick and have severe or continuing vomiting or diarrhea while taking this medicine, check with your doctor. These problems may cause you to lose additional water and potassium and lead to low blood pressure.

Before having any kind of surgery (including dental surgery) or emergency treatment, inform the doctor or dentist that you are taking this medicine.

Before taking any medical tests, tell the doctor you are taking this drug. It may affect the test results.

If you are taking this medicine for high blood pressure, do not take any other medicine unless your have discussed it with your doctor. This includes nonprescription drugs--particularly those for appetite control, asthma, colds, cough, hay fever, or sinus problems--some of which contain ingredients that may increase your blood pressure.

If you are taking triamterene and hydrochlorothiazide, do not change brands without first checking with your doctor. If you refill your medicine and it looks different, check with your pharmacist.

FDA / FDA Consumer