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Diuretics are a class of medications that promote the production of urine. There are several types of diuretics. All diuretics increase water excretion, but different types do so in different ways.

Diuretics can be used in the treatment of hypertension, heart failure, liver cirrhosis, and certain kidney diseases. Loop diuretics such as furosemide, torsemide, and ethacrynic acid cause a substantial diuresis by inhibiting reabsorption of sodium, leading to excretion of water.

There are many types of diuretics, each of them working differently to accomplish the same purpose of increasing urine output. Due to their different action mechanisms, different classes of diuretics can cause different side effects. Therefore, it is important to discuss treatment options with a medical professional to find the best drug that fits your requirements with fewer amount of side effects. Below are 10 side effects associated with diuretics.

Side Effect #1: Dehydration


Dehydration occurs when there is a total body water deficit along with the disruption of metabolic processes. This is when free water intake is less than free water loss due to high environmental pressure, disease, or exercise. Most individuals easily tolerate about 3 to 4 percent of total body water deficit without experiencing much effect.

Some causes of dehydration include vomiting, diarrhea, and excessive sweating. It can also occur as a side effect of diuretics as the medication causes excretion of fluid through the urinary tract. This is not a common finding in patients taking diuretics as they are usually able to replenish their water loss orally, but some diuretics such as mannitol which causes osmotic diuresis, are associated with dehydration.


Side Effect #2: Hypotension

Hypotension or low blood pressure occurs when the systolic blood pressure is less than 90 mmHg or if the diastolic blood pressure drops less than 60 mmHg. In practice, hypotension occurs only if there are noticeable symptoms. Hypotension can cause the affected person to feel dizzy or faint. There can also be shortness of breath, chest pain, headache, and fatigue.

Causes of hypotension include hormonal changes, low blood volume, anemia, side effect of medications, and dilation of the blood vessels. Diuretics can cause hypotension as they lead to fluid loss resulting in hypovolemia.


Side Effect #3: Hypokalemia

Hypokalemia occurs when the serum potassium levels are low. Mild cases do not generally cause symptoms. More serious cases will lead to leg cramps, tiredness, constipation, and weakness. It can also cause an abnormal heart rhythm, which can lead to cardiac arrest.

Causes include dialysis, vomiting, diarrhea, hyperaldosteronism, hypomagnesemia, steroids, and diuretics (furosemide). Hypokalemia occurs when the serum potassium levels are less than 3.5 mmol/l.

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Side Effect #4: Hyperkalemia

Hyperkalemia describes the elevated levels of serum potassium. Normal levels range from 3.5 to 5.0 mmol/l. Hyperkalemia occurs when the serum potassium levels are above 5.5mmol/l.

Symptoms of hyperkalemia include muscle pain, palpitations, numbness, muscle weakness, abnormal heart rhythm, and death. Common causes of hyperkalemia include kidney failure and rhabdomyolysis. Medications that can cause hyperkalemia are nonsteroidal anti-inflammatory drugs (NSAIDs), angiotensin-converting enzyme (ACE) inhibitors and, diuretics such as spironolactone which is a potassium-sparing diuretic.

Side Effect #5: Hyponatremia

Hyponatremia refers to low sodium levels in the blood or it can be defined as having a sodium concentration of less than 135 mmol/L. Depending on the severity of hyponatremia, symptoms may be absent, mild, or severe. Mild symptoms of hyponatremia include nausea, headaches, decreased ability to think, and poor balance. When severe, symptoms proceed to include seizures, confusion, and coma.

Causes of hyponatremia are classified based on the individual’s body fluid status. Examples include diarrhea, diuretics, sweating, vomiting, hypothyroidism, and adrenal insufficiency. It can also occur as a side effect of diuretics, especially osmotic ones like mannitol and potassium-sparing diuretic like spironolactone.


Side Effect #6: Metabolic Alkalosis

Metabolic alkalosis is the condition where the pH is elevated beyond the normal range (pH 7.35–7.45). The mechanism of metabolic alkalosis involves decreased concentration of hydrogen ions or increased bicarbonate concentrations.

Signs and symptoms of metabolic alkalosis include neuromuscular irritability, abnormal sensations, abnormal heart rhythms, tetany, seizures, coma, and confusion that waxes and wanes. Some examples of conditions that may cause metabolic alkalosis are severe vomiting, side effects of diuretics (thiazides and loop diuretics), congenital chloride diarrhea, and cystic fibrosis.


Side Effect #7: Metabolic Acidosis

Metabolic acidosis is a condition that occurs when there is excessive acid production or when there is inadequate acid removal through the kidneys. Metabolic acidosis can result in acidemia. This occurs when the blood pH is less than 7.35 due to increased hydrogen ion production or inability to form bicarbonate.

There are many causes for metabolic acidosis. Complications of metabolic acidosis are severe, leading to coma and death. Symptoms include altered mental status, headache, palpitations, chest pain, nausea, vomiting, muscle weakness, joint pain, and bone pain. Kussmaul respirations may also occur. Causes of metabolic acidosis include ketoacidosis, chronic kidney failure, infection, lactic acidosis, side effects of diuretics, and intoxication from salicylates, formaldehyde, isoniazid, sulfates, and metformin.

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Side Effect #8: Hypercalcemia

Hypercalcemia occurs when the serum calcium levels are high. It can be defined as having serum calcium levels that are greater than 2.6 mmol/l. Mild hypercalcemia does not usually produce symptoms. Those with symptoms may experience confusion, abdominal pain, depression, bone pain, weakness, abnormal heart rhythm, kidney stones, or cardiac arrest.

Most cases of hypercalcemia are due to primary hyperthyroidism or cancer. Other possible causes include tuberculosis, sarcoidosis, multiple endocrine neoplasia, Paget’s disease, familial hypocalciuric hypercalcemia, and medications such as lithium and diuretics. The diuretic implicated in this case would be hydrochlorothiazide.


Side Effect #9: Hyperuricemia

Hyperuricemia occurs when the level of uric acid in the blood is abnormally high. The level of urate depends on the balance of purines available in food. There are various causes of hyperuricemia such as insulin resistance, hypertension, genetics, iron overload, renal insufficiency, diet, obesity, hypothyroidism, excessive alcohol use, and use of diuretics.

Hyperuricemia occurs when there is increased uric acid production, decreased uric acid excretion, and mixed. It is estimated that only about 30 percent of individuals with hyperuricemia experience symptoms. Hyperuricemia can lead to gout and kidney stones. This side effect is usually associated with thiazide diuretics like hydrochlorothiazide.

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Side Effect #10: Fatigue

Fatigue describes a gradual feeling of tiredness that can be alleviated by rest. Fatigue can be divided into physical and mental fatigue. Physical fatigue refers to the temporary inability of the muscle to achieve maximum physical performance while mental fatigue is the transient inability to maintain optimal cognitive performance. Fatigue can manifest as lethargy or somnolence.

It is a common and nonspecific symptom that can be seen in dehydration, infection, cancer, sleep deprivation, overworking, stress, and pregnancy. It can also be a side effect of some medications such as beta blockers and diuretics.

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