Diuretics: Types and Uses in Treatment

Diuretics, also called ‘water pills’, are a class of medicines that are used to reduce high blood-pressure. Fluid retention is a symptom or consequence of several health conditions. This means, salts and water start accumulating in blood-vessels in one or more parts of the body. This increases the pressure in them, and hence the risk of certain cardiovascular conditions. In such a scenario, diuretics are given to the patient. These medicines help remove the excess water and salt in the body, and eliminate it through the urine. Incidentally, diuretics can also be used to treat certain ailments other than hypertension (high blood pressure) which is why they have gained prominence in the last couple of decades.

Conditions for which diuretics are prescribed

• Hypertension or high blood-pressure
• Heart failure
• Cardiomyopathy (a chronic disease of the heart muscle)
• Swelling in tissues of the body (edema)
• Pulmonary edema (fluid accumulation in the lungs)
• Ascites (fluid build-up in the abdomen)
• Renal or kidney failure
• Liver failure
• Nephrotic syndrome (kidney disease marked by edema and loss of protein into the urine)
• Glomerulonephritis (inflammation of the tiny filters in the kidneys)
• Kidney stones
• Diabetes insipidus (marked by production of large quantities of dilute urine)
• High intraocular pressure (high pressure in the eyes due to fluid build-up there)
• High intracranial pressure (high pressure in the area surrounding the brain due to fluid build-up there)
• Glaucoma (diuretics help reduce the pressure in the eye)

Diuretics are also given along with other medication (called adjunctive therapy) for:

• Edema associated with congestive heart failure
• Corticosteroid and estrogen therapy
• Cirrhosis of the liver

How do Diuretics work

One of the primary functions of the kidneys is to ensure a careful balance between the levels of sodium (salt is sodium chloride) and water in the body. This means, if sodium chloride is eliminated from the body, water is also eliminated along with them. Similarly, if sodium chloride is retained in the body due to one or more health conditions, water is also retained. They always stick together.

Diuretics are a class of medicines that remove the excess sodium from the body through the urine. As Sodium carries water along, there is more urination (called diuresis).

The body always tries to maintain the balance of sodium and water, from both dietary intake and medication consumed by the person. So if the person is consuming more sodium through the diet than what is leaving the body, the consequences are hypertension, edema and pulmonary edema. Similarly, prolonged use of diuretics can cause dehydration (as more and more water is eliminated from the body), low blood pressure and kidney failure.

Types

There are 5 types of diuretics with the first 3 being more prominent.

• Loop diuretics: These are the most popular, and most powerful class of diuretic. These work by preventing reabsorption of sodium and chloride in the loop of Henle (a portion of the renal tubule) in the kidneys. This ensures sodium and chloride are eliminated effectively.

Examples include: bumetanide (Bumex), torsemide [(Demadex) (oral or injection)], furosemide [(Lasix) (oral or injection)] and ethacrynate (Edecrin)

• Thiazide diuretics: These ensure sodium and chloride are eliminated in approximately equivalent amounts. This is achieved by inhibiting the reabsorption of sodium and chloride in the distal convoluted tubules of the kidneys.

Examples include: chlorothiazide [(Diuril) (oral or sodium injection)], metolazone (Zaroxolyn, Diulo, Mykrox), chlorthalidone (Hygroton), methyclothiazide (Enduron), indapamide (Lozol) and hydrochlorothiazide (Hydrodiuril)

• Potassium-sparing diuretics: In the distal tubule of the kidneys, under normal conditions, potassium is excreted into the urine that is being formed, while sodium is reabsorbed. These actions happen in tandem. Now, potassium is required for the body, and excess removal of potassium can lead to health conditions. So potassium-sparing diuretics are used to reduce sodium reabsorption at the distal tubule, which in turn decreases potassium elimination. This class of diuretics when used alone are weak, so they are given along with thiazide and loop diuretics (combination therapy).

Examples include: Amiloride hydrochloride, triamterene (Dyrenium) and spironolactone (Aldactone)

• Carbonic Anhydrase Inhibitors: These achieve increased excretion of sodium, chloride salts, water, potassium and bicarbonate from the renal tubules of the kidneys.

Examples include: Acetazolamide Tablets, Acetazolamide Injection and Methazolamide

• Osmotic diuretics: These are substances with a low-molecular-weight, so they are easily filtered out of the blood and into the tubules where they begin to accumulate. These prevent the reabsorption of water, sodium, and chloride by the kidneys.

Examples include: glycerin (Glycerol), Urea, Isosorbide and Mannitol IV

Risks / Complications / Disadvantages

In-spite of their wide usage, diuretics come with their own side-effects, risks, complications and disadvantages if they are used for long, or consumed in high doses. However, doctors treating the patient are aware of this, and will take the necessary caution. So this section is just for your knowledge.

Due to fluid imbalance

• Dehydration
• Dry mouth and thirst
• Hypotension (low BP)
• Confusion
• Weakness
• Drowsiness
• Lethargy
• Seizures
• Restlessness
• Muscular fatigue
• Muscle pains or cramps
• Tachycardia (rapid heart-beat)
• Oliguria (decreased or no urine-output)
• Gastrointestinal (GI) disturbances

Due to low sodium

• Thiazide diuretics can cause low sodium in the body which can lead to neurological damage and death.

Due to high uric acid

Increased elimination of water can concentrate uric acid in the body. This leads to

• Muscle pain and muscle fatigue
• Gout

Due to drug interactions

• Thiazide Diuretics given along with anti-diabetes medicines can cause the latter’s depletion from the body, so their dosage may have to be increased.
• Digoxin given for heart-failure and arrhythmias when combined with thiazide or loop diuretics can cause depletion of potassium in the body which leads to irregular heart-beat, weakness and cramps.
• Lithium given for stabilizing mood and treating neurological disorders when combined with diuretics can cause lithium to accumulate in the body, leading to headache, increased thirst, nausea or vomiting, dry mouth, changes in appetite, diarrhea, dizziness, drowsiness and hand tremors.
• Potassium-sparing diuretics when given along with ACE Inhibitors and NSAIDs can cause hyperkalemia or high levels of potassium in the blood. This can lead to slow heart-rate (bradycardia), muscle weakness and fatigue.
• Diuretics when combined with medication given for heart ailments can cause electrolyte imbalances in the body including low levels of potassium.

Who should not be given diuretics

There are certain classes of patients who are not advised diuretics due to complications resulting from the same. The doctors are aware of this and will cover this in the initial examination.

• Pregnant women
• Lactating/breastfeeding mothers
• People with kidney disease
• People with liver disease
• Young children
• Women with menstrual problems
• People suffering from dehydration
• People suffering from polyuria (excess urine output)

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Reviewed by Dr Suresh S Venkita, Group Medical Director, Kauvery Hospitals

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Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai, Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and pediatric trauma care.

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NOTE: Take medications only when prescribed by your doctors, self-medication must be avoided under any circumstances.

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