Hypothiazid (Hydrochlorothiazide)

Hydrochlorothiazide is indicated for several cardiovascular and renal conditions that involve fluid retention or elevated arterial pressure.

• Hypertension: helps lower systolic and diastolic blood pressure, reducing cardiovascular risk.
• Edema associated with heart failure: promotes diuresis to decrease fluid overload and improve symptoms.
• Edema due to liver cirrhosis: assists in removing excess ascitic fluid and peripheral swelling.
• Edema due to renal disease: facilitates sodium and water excretion to manage fluid retention.

• Hydrochlorothiazide acts on the distal convoluted tubule of the nephron by inhibiting the Na⁺/Cl⁻ symporter. This blockade reduces sodium reabsorption, leading to increased urinary excretion of sodium and water. The resulting decrease in extracellular fluid volume lowers cardiac output and systemic vascular resistance, contributing to blood pressure reduction and edema relief.

Hydrochlorothiazide may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Increased urination: more frequent need to void.
• Electrolyte imbalance: low potassium or sodium levels.
• Dizziness or light‑headedness, especially on standing.
• Headache: mild to moderate intensity.
• Fatigue: general feeling of tiredness.
• Mild gout attacks: elevated uric acid may trigger symptoms.

Serious or Rare Side Effects

• Severe electrolyte disturbances: hypokalemia or hyponatremia requiring medical attention.
• Acute renal failure: sudden loss of kidney function.
• Pancreatitis: inflammation of the pancreas.
• Severe allergic reactions: rash, swelling, or anaphylaxis.
• Blood dyscrasias: rare blood cell abnormalities such as agranulocytosis.

Before initiating therapy, clinicians should evaluate patient‑specific factors and monitor key parameters.

• Monitor electrolytes: check serum potassium and sodium regularly.
• Assess renal function: evaluate creatinine and glomerular filtration rate before and during treatment.
• Avoid in severe renal impairment: contraindicated when GFR is below 30 mL/min.
• Caution in gout: may precipitate hyperuricemia and gout flares.
• Use with caution in diabetes: diuretic effect can affect glucose control.
• Store at room temperature: keep in the original container, protect from moisture and light.

Hydrochlorothiazide can alter the pharmacokinetics or pharmacodynamics of several co‑administered medicines.

Major Interactions (Avoid)

• Lithium: increased lithium concentrations may lead to toxicity.
• NSAIDs: may reduce diuretic efficacy and impair renal function.
• ACE inhibitors or ARBs: combined use can cause severe potassium loss.
• Digitalis glycosides: electrolyte shifts can enhance digitalis toxicity.

Moderate Interactions (Monitor Closely)

• Corticosteroids: additive fluid‑retaining effects.
• Antidiabetic agents: may require dose adjustment due to altered glucose handling.
• SSRIs and other antidepressants: potential for hyponatremia, especially in the elderly.