Diuretics are used to treat several conditions in medicine including heart failure, high blood pressure, liver disease and some types of kidney disease. The use of some diuretics is also indicated in cases of overdose or poisoning, to help increase the excretion of certain substances from the patient’s body. Diuretics may also be abused by people suffering from eating disorders as a way of helping them to lose weight. Some examples of the different types of diuretics available and indications for their use are described below.
Carbonic anhydrase inhibitors
These agents may be taken as tablets, eye drops or in the form of an injection. Carbonic anyhdrase inhibitors may be used to treat glaucoma, a condition that leads to increased intraocular pressure or raised pressure of the eye fluid. These drugs reduce the secretion of aqueous humor by suppressing carbonic anhydrase activity in the ciliary body, therefore reducing the intraocular pressure. Carbonic anhydrase inhibitors are also used to correct acute mountain sickness, a condition that can lead to weakness, dizziness, headaches, sleeplessness and nausea.
Drugs of this class include furosemide, ethacrynic acid, torsemide and bumetanide. These drugs inhibit the reabsorption of sodium in the nephron, therefore increasing the amount of water excreted in the urine. This water would normally flow back into the extracellular fluid along with the sodium.
Some examples of the conditions these agents are used to treat include:
- Acute pulmonary edema
- Acute left ventricular failure or heart failure
- Most types of edema or fluid accumulation
- Acute rise of blood calcium or hypercalcemia
- Acute rise of blood potassium or hyperkalemia
- Acute renal failure
- Anion disease
These drugs inhibit the sodium-chloride sympoter in the distal convoluted tubule, causing water to be retained in the urine. One example of a drug in this class is hydrochlorothiazide. The main conditions these agents are used to treat include:
- Hypertension or high blood pressure
- Heart failure
- Kidney stones
- Nephrogenic diabetes insipidus
Osmotic diuretics inhibit the reabsorption of sodium and water, increasing the osmolarity of the blood and the renal filtrate. Examples of these agents include isosorbide and mannitol, which may be used for the following:
- Reduction of intracranial pressure or pressure within the skull
- Treatment of oliguric renal failure
- Transportation of drugs straight to the brain
Potassium sparing diuretics
These agents act as diuretics without causing potassium to be lost in the urine. Spironolactone is the most widely used of these drugs and is indicated in the following conditions:
- Heart failure – The agent promotes the loss of fluid and salt as well as benefiting the cardiac muscles by preventing the pathological remodelling associated with heart failure.
- Kidney disease
- Liver disease – Liver disease is often associated with edema and ascites along with elevated portal hydrostatic pressure.
Reviewed by Sally Robertson, BSc