Hydrochlorothiazide is a widely prescribed thiazide diuretic, recognized for its efficacy in managing hypertension and edema. It functions by promoting the excretion of sodium and water from the body, thereby reducing blood volume and peripheral vascular resistance. This medication is often utilized as a first-line treatment or in combination with other antihypertensive agents. Its well-established safety profile and cost-effectiveness make it a cornerstone in cardiovascular and renal therapeutic regimens.

Features

• Active ingredient: Hydrochlorothiazide
• Drug class: Thiazide diuretic
• Available in tablet form (commonly 12.5 mg, 25 mg, 50 mg)
• Oral administration, typically once daily
• Onset of diuretic action within 2 hours, peak effect at 4–6 hours
• Duration of action: 6–12 hours
• Bioavailability: approximately 50–70%
• Protein binding: 40–60%
• Metabolism: minimal hepatic metabolism
• Excretion: primarily renal

Benefits

• Effectively lowers systolic and diastolic blood pressure, reducing the risk of stroke, myocardial infarction, and heart failure.
• Reduces edema associated with congestive heart failure, hepatic cirrhosis, and renal dysfunction.
• May be used in combination with other antihypertensive agents for synergistic effects.
• Helps prevent kidney stones in patients with hypercalciuria by reducing urinary calcium excretion.
• Cost-effective compared to many newer antihypertensive medications.
• Well-tolerated with a long history of clinical use and extensive safety data.

Common use

Hydrochlorothiazide is primarily indicated for the management of hypertension, either as monotherapy or in combination with other antihypertensive drugs such as ACE inhibitors, angiotensin II receptor blockers, or beta-blockers. It is also used to treat edema due to various causes, including congestive heart failure, cirrhosis of the liver, corticosteroid and estrogen therapy, and renal dysfunction. Additionally, it is employed in the treatment of diabetes insipidus and to prevent calcium-containing kidney stones in patients with idiopathic hypercalciuria.

Dosage and direction

The dosage of hydrochlorothiazide must be individualized based on the patient’s condition and response. For hypertension, the usual initial dose is 12.5–25 mg once daily. The dosage may be increased to 50 mg once daily or in divided doses if necessary. For edema, the initial dose is 25–100 mg daily, which may be administered as a single dose or in divided doses. Maintenance therapy may be on an intermittent schedule (e.g., every other day). It is generally recommended to take hydrochlorothiazide in the morning to avoid nocturia. Dosage adjustments are necessary in patients with renal impairment.

Precautions

Patients should be advised to avoid dehydration and ensure adequate fluid intake. Electrolyte levels (particularly potassium, sodium, and magnesium) should be monitored periodically, as hydrochlorothiazide can cause hypokalemia, hyponatremia, and hypomagnesemia. Use with caution in patients with impaired renal function or severe liver disease. May exacerbate or activate systemic lupus erythematosus. Photosensitivity reactions may occur; patients should use sun protection. Orthostatic hypotension may occur, especially in volume-depleted patients. Discontinue if pancreatitis occurs.

Contraindications

Hydrochlorothiazide is contraindicated in patients with anuria or known hypersensitivity to hydrochlorothiazide or other sulfonamide-derived drugs. It should not be used in patients with refractory hypokalemia, hypercalcemia, or Addison’s disease. Contraindicated in combination with dofetilide due to risk of severe hypokalemia and life-threatening arrhythmias.

Possible side effect

Common side effects include dizziness, headache, gastrointestinal disturbances (nausea, vomiting, diarrhea), hypokalemia, hyperuricemia, and hyperglycemia. Less frequently, orthostatic hypotension, photosensitivity, impotence, and pancreatitis may occur. Rare but serious adverse effects include leukopenia, agranulocytosis, aplastic anemia, thrombocytopenia, hepatic dysfunction, and anaphylactic reactions.

Drug interaction

Hydrochlorothiazide may increase the risk of lithium toxicity by reducing renal clearance. Concurrent use with other antihypertensive agents may potentiate hypotension. May enhance the hyperglycemic effect of diazoxide. Corticosteroids and ACTH may increase the risk of hypokalemia. NSAIDs may reduce the diuretic and antihypertensive effects. Cholestyramine and colestipol may reduce absorption. May potentiate the effects of neuromuscular blocking agents. Alcohol, barbiturates, or narcotics may potentiate orthostatic hypotension.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next dose. In that case, skip the missed dose and resume the usual dosing schedule. Do not double the dose to catch up.

Overdose

Symptoms of overdose include profound electrolyte disturbances (hypokalemia, hyponatremia), dehydration, hypotension, and circulatory collapse. Treatment is supportive and symptomatic, including gastric lavage or activated charcoal if ingestion was recent, correction of fluid and electrolyte imbalances, and management of hypotension with intravenous fluids and vasopressors if necessary. Hemodialysis is not effective due to high protein binding.

Storage

Store at room temperature (20–25°C or 68–77°F), in a tightly closed container, away from light and moisture. Keep out of reach of children and pets. Do not use after the expiration date printed on the packaging.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Always consult a healthcare professional before starting, changing, or discontinuing any medication. The prescribing physician should determine the appropriate dosage and monitor for adverse effects based on individual patient factors.

Reviews

Hydrochlorothiazide has been extensively studied and is generally well-regarded in the medical community for its efficacy in hypertension and edema management. Clinical trials, such as those from the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), have demonstrated its effectiveness in reducing cardiovascular events. Many patients report satisfactory blood pressure control with minimal side effects, though some note issues with electrolyte imbalances or increased urination. It remains a foundational therapy in guidelines from organizations like the American Heart Association and the European Society of Cardiology.