Different classes of diuretics have different side effect profiles. The types of side effects caused by a diuretic depends on the drug’s mechanism of action. Some of the side effects caused by the different classes of diuretic are described below:

Carbonic anhydrase inhibitors

An example of a drug in this class is acetazolamide. Some of the side effects include:

• Hyperchloremic metabolic acidosis caused by loss of plasma bicarbonate
• Kidney stones due to increased phosphate and calcium excretion
• Low potassium level (hypokalemia)
• Drowsiness
• Neurotoxicity
• Allergic or hypersensitivity reactions

Loop diuretics

Examples of drugs in this class include furosemide, ethacrynic acid and bumetanide. Some of the side effects associated with the use of loop diuretics include:

• Hypokalemic metabolic alkalosis due to loss of potassium and increased alkalinity of the blood
• Ototoxicity or damage to hearing. This damage may be reversible if the drug is stopped.
• High blood levels of uric acid predisposing to attacks of gout
• Hypomagnesemia or low magnesium level
• Allergic or hypersensitivity reactions
• Dehydration
• High blood levels of calcium or hypercalcemia

Thiazide diuretics

An example of a thiazide diuretic is hydrochlorothiazide. Some of the side effects include:

• Hypokalemic metabolic alkalosis
• Hyperuricemia or raised blood uric acid, predisposing to gout
• Impaired carbohydrate or glucose tolerance leading to high blood sugar
• Hyperlipidemia or increased blood lipids (cholesterol and lipoproteins)
• Hyponatremia or low blood sodium
• Allergic or hypersensitivity reactions caused by the sulfonamide component of these agents. Reactions include dermatitis, skin rash, photo-dermatitis (light reactions on skin), hemolytic anemia (breakdown of the red blood cells), thrombocytopenia (low platelet counts) and acute necrotizing pancreatitis.
• Weakness and tiredness
• Paresthesias or numbness of the limbs
• Impotence

Potassium-sparing diuretics

These drugs can be divided into two classes, which include the aldosterone antagonists such as apironolactone and sodium channel blockers such as triampterene and amiloride. Some of the side effects include:

• Hyperkalemia or rise in blood potassium levels
• Hyperchloremic metabolic acidosis
• Gynecomastia or breast enlargement in males
• Erectile dysfunction
• Benign prostatic hyperplasia
• Acute renal failure
• Kidney stones

Osmotic diuretics

Examples of these agents include isosorbide and mannitol. Some of the side effects include:

• Extracellular volume expansion. This can be a serious problem in people with heart failure or pulmonary edema.
• Headache
• Nausea and vomiting
• Dehydration and loss of free water
• Hypernatremia or increased sodium levels