Hydrochlorothiazide

At a Glance

What is Hydrochlorothiazide?

Hydrochlorothiazide (HCTZ) is a short-acting thiazide diuretic commonly prescribed to manage high blood pressure (hypertension). It is also used as add-on (adjunctive) therapy for edema (fluid retention) caused by heart failure, liver cirrhosis, and corticosteroid or estrogen therapy. It has also been found useful for edema due to kidney problems such as nephrotic syndrome, acute glomerulonephritis and chronic renal failure. Whether it is suitable in kidney disease is decided by the treating doctor.

How Hydrochlorothiazide Works

Hydrochlorothiazide acts on the distal tubule of the kidneys, where it blocks the reabsorption of sodium and chloride. This increases the excretion of salt and excess water in urine, which reduces the amount of fluid in the body and relieves swelling. It does not usually lower normal blood pressure, and the exact way it lowers high blood pressure is not fully understood.

After an oral dose, urine output begins within about 2 hours, peaks at around 4 hours, and lasts roughly 6 to 12 hours.

When Hydrochlorothiazide Is Used

• Hypertension: Commonly used for high blood pressure, either alone or together with other blood pressure medicines.
• Edema: Helps reduce swelling from fluid build-up in conditions such as heart failure, cirrhosis or kidney disease. The doctor decides case by case whether it is appropriate.
• Kidney stones (off-label): Not an approved indication, but doctors sometimes prescribe it to reduce urinary calcium in people with recurrent calcium kidney stones. Evidence is mixed, and a large 2023 trial (the NOSTONE trial) found no reduction in symptomatic stone recurrence. Guidelines still allow doctors to offer thiazides to some people with high urinary calcium.

Dosage and How to Take It

Doctors use the smallest dose that works. The doses below follow US prescribing information and are general information only. The final dose is decided by your doctor.

• Hypertension (adults): The usual starting dose is 25 mg once daily. The doctor may increase it to 50 mg daily, as a single dose or two divided doses. Doses above 50 mg are often linked with marked drops in potassium. When combined with other blood pressure medicines, doses above 50 mg are usually not needed.
• Edema (adults): 25 to 100 mg daily as a single or divided dose. Many people respond to intermittent therapy (alternate days, or 3 to 5 days a week), which makes excessive response and electrolyte imbalance less likely. Your doctor chooses whether a daily or intermittent schedule suits you.
• Children: Dosing is based on age, weight, the condition being treated and clinical condition, and must be set by the child’s doctor. US prescribing information gives a usual range of 1 to 2 mg/kg per day in one or two divided doses, not exceeding 37.5 mg daily in infants up to 2 years or 100 mg daily in children aged 2 to 12 years. Infants under 6 months may need up to 3 mg/kg per day in two divided doses. Parents and caregivers should not calculate, adjust or change a child’s dose themselves, and adult doses must never be used for children.

Take this medicine only as advised by your doctor or healthcare professional. Do not start, stop, or change the dose on your own.

Side Effects

Common or important side effects include:

• Dizziness, headache and weakness
• Low blood pressure, including a drop when standing up (made worse by alcohol)
• Nausea, vomiting, diarrhea, constipation and stomach cramping
• Muscle cramps or spasms
• Low potassium and other electrolyte imbalances, which can cause dry mouth, thirst, weakness and lethargy
• Raised blood sugar (important for people with diabetes) and raised uric acid, which can trigger gout
• Sensitivity to sunlight and temporary blurred vision

Serious side effects are less common and need prompt medical attention:

• Severe allergic or skin reactions, including Stevens-Johnson syndrome
• Yellowing of the skin or eyes (jaundice) or inflammation of the pancreas
• Blood disorders such as low white cells or platelets
• Kidney problems
• Long-term use has been linked with an increased risk of non-melanoma skin cancer. This risk is associated with cumulative (total) exposure over time, so protect your skin from excessive sunlight and report any new or changing skin lesions to your doctor.

Precautions and Monitoring

• Do not use if you pass no urine (anuria), or if you have had an allergic reaction to hydrochlorothiazide or a related sulfonamide-derived medicine. Tell your doctor about any previous sulfonamide (“sulfa”) allergy before treatment so the doctor can judge whether it matters in your case.
• Use with caution in liver disease, as small changes in fluid and electrolyte balance can be harmful, and in people with gout or lupus (it may worsen or activate lupus).
• If you have diabetes, your doctor may need to adjust your diabetes medicine.
• Thiazides should be stopped before tests of parathyroid function, so tell your doctor you take it.

Kidney function

Hydrochlorothiazide is eliminated by the kidneys. Doctors consider kidney function before and during treatment. In people with kidney disease, thiazides may raise waste products in the blood (azotemia), and the medicine’s effects can build up when kidney function is reduced. It should be used with caution in severe kidney disease, and your doctor may stop it or choose a different approach if kidney function worsens. Only your treating doctor can decide whether hydrochlorothiazide is appropriate for you.

Monitoring

Depending on your health, doctors may check blood potassium, sodium and other electrolytes, kidney function, blood pressure, and blood sugar (in people with diabetes). They may also check uric acid when gout is a concern. Monitoring is not identical for every person.

Drug Interactions

• Alcohol, barbiturates and opioid pain medicines: can worsen dizziness or low blood pressure on standing.
• Other blood pressure medicines: can add to its effect, so the doctor may adjust treatment.
• Diabetes medicines (tablets and insulin): the dose may need adjusting.
• Cholestyramine and colestipol: reduce absorption of hydrochlorothiazide.
• Corticosteroids and ACTH: can increase potassium loss.
• Lithium: diuretics reduce lithium clearance and raise the risk of lithium toxicity, so they are generally not given together.
• NSAIDs (such as ibuprofen or diclofenac): can reduce its diuretic and blood-pressure-lowering effect in some people, so your doctor may watch your response. If you have kidney problems, check with your doctor before using them.

Tell your doctor and pharmacist about all prescription medicines, over-the-counter medicines, supplements and herbal products you take. This list is not complete.

Pregnancy and Breastfeeding

Routine use of diuretics during normal pregnancy is not appropriate, and swelling from normal pregnancy is usually managed without diuretics. Hydrochlorothiazide crosses the placenta, and thiazide exposure has been associated with jaundice and low platelet counts (thrombocytopenia) in newborns. Evidence from well-controlled studies in pregnant women is limited. It may still be used when swelling has a medical cause, and your doctor weighs the benefits and risks. Do not use it in pregnancy unless your doctor advises it.

Hydrochlorothiazide is excreted into breast milk. Because of the potential for serious side effects in a breastfed infant, the decision to continue the medicine or breastfeeding depends on your situation and on how important the medicine is for you. Your doctor will guide you, and you should not stop either on your own.

Brands, Strengths and Approximate Price in India

Examples of hydrochlorothiazide brands available in India include Aquazide, Hydrazide and Hydride. This is not an exhaustive list. Hydrochlorothiazide is the generic name.

Approximate price in India: ₹5–₹24 per strip of 10 tablets (12.5 mg and 25 mg).

Prices shown are printed MRPs, not discounted online prices. They may vary by brand, strength, pack size, pharmacy and location.

How HealthPil Can Help

Medicines should be started, adjusted, or stopped only under the guidance of a qualified healthcare professional. If you have questions about this medicine, its side effects, or your treatment plan, you can consult a doctor through HealthPil, including cardiologists and nephrologists for blood pressure and fluid retention.