Drug Therapy: Diuretics

Diuretics reduce the amount of salt and water in the body. As the kidneys filter the excess water from the blood, the volume of blood the heart has to pump is reduced, causing blood pressure to go down.

Diuretics are given when the have congestive high blood pressure, swelling or water retention (edema) or heart failure. They may also be prescribed for certain kinds of kidney or liver disease. Diuretics can be very useful for people who are older or obese.

There are three types of diuretics:

  • Loop-acting diuretics, such as Bumex®, Demadex®, Edecrin® or Lasix®. These cause the kidneys to get rid of more urine, lowering the amount of water in the body and the blood pressure.
  • Potassium-sparing diuretics, such as Aldactone®, Dyrenium® or Midamor®. These drugs reduce the amount of water in the body, but while other diuretics cause the body to lose potassium in the process, this type does not. This type of diuretic is often prescribed with another diuretic because, while it spares potassium, it does not control blood pressure as well as thiazide diuretics do.
  • Thiazide diuretics, such as Aquatensen®, Diucardin® or Trichlorex®. This type of diuretic reduces the amount of salt and water in the body. It is also the only type of diuretic that widens the blood vessels to lower blood pressure. Thiazide diuretics are often the first drug given to treat high blood pressure.
If diuretics are prescribed, the doctor should be made aware of any other drug, vitamin, mineral or herbal supplement the patient is taking, especially:
  • Antidepressants, particularly when taking thiazide or loop-acting diuretics
  • Clyclosporine, particularly if taking a potassium-sparing diuretic
  • Digitalis, particularly for patients with low potassium levels
  • Lithium
  • Other medications for high blood pressure
The doctor should be told if the patient has:
  • A tendency to become dehydrated easily
  • Allergies to other medicines
  • Been thinking about becoming pregnant or already is pregnant
  • Diabetes because thiazide and loop-acting diuretics can increase the blood sugar levels
  • Gout or are a high risk of developing gout, especially if the doctor is considering prescribing a thiazide diuretic
  • Kidney problems
  • Lupus because thiazide diuretics can make this worse
  • Pancreatitis because loop-acting diuretics make this worse
To learn more about these types of drugs and their side effects, click on the links below:
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