HCTZ (Hydrochlorothiazide)

HCTZ (hydrochlorothiazide) is a prescription drug used to treat high blood pressure and fluid retention (edema). It belongs to a class of medicines called thiazide diuretics, often referred to as water pills. It helps your kidneys remove extra salt and water through urine, which can lower blood pressure and reduce stress on the heart and blood vessels. HCTZ may also be used for swelling caused by heart failure, liver disease, kidney problems, or certain medicines.

Directions

Take HCTZ by mouth, usually once per day in the morning so it is less likely to make you urinate at night. You can take it with or without food.

Always take it exactly as prescribed. Drink enough water and get any recommended blood tests on schedule. The dose depends on what it is treating and how your body responds.

For adults with high blood pressure, the usual starting dose is 25 mg once daily, which may be increased to 50 mg daily.

For edema, adults usually take 25 to 100 mg per day, either daily or on a schedule set by a healthcare provider.

For children, the dose is based on body weight and age. Children under 2 may take up to 37.5 mg per day, while children ages 2 to 12 may take up to 100 mg per day.

Ingredients

The active ingredient is hydrochlorothiazide. The inactive ingredients may include dibasic calcium phosphate dihydrate, FD and C Yellow No. 6, lactose monohydrate, magnesium stearate, pregelatinized starch, and sodium starch glycolate.

Cautions

Before using this medication, you may want to consult a healthcare provider about the following:

• Any existing health conditions
• Any allergies
• A list of all medications currently being taken

Use HCTZ with caution if you have kidney disease or impaired kidney function. The drug can build up in the body and may worsen kidney problems.

Use with caution if you have liver problems, since small changes in fluid and electrolyte balance may cause a hepatic coma in people with severe liver disease.

HCTZ can cause low potassium, low sodium, low magnesium, and high calcium levels. Warning signs of electrolyte imbalance include dry mouth, thirst, weakness, drowsiness, restlessness, confusion, muscle cramps, fast heartbeat, and nausea or vomiting.

HCTZ can increase blood sugar levels. People with diabetes may need their insulin or oral diabetes medications adjusted.

HCTZ can increase uric acid levels and may trigger a gout flare in people at risk of gout.

In rare cases, HCTZ can cause sudden eye problems, including acute short-sightedness (myopia) and acute angle-closure glaucoma, usually within hours to weeks of starting the medication.

Long-term use of HCTZ has been linked to a higher risk of non-melanoma skin cancers, especially squamous cell carcinoma. Protect skin from too much sun, use sunscreen and protective clothing, and have regular skin checks.

Tell your healthcare provider about all other medications you take. HCTZ may interact with medications like lithium, NSAIDs, corticosteroids, other blood pressure medicines, digoxin, diabetes medications, cholestyramine or colestipol resins, and muscle relaxants.

HCTZ may also activate or worsen systemic lupus erythematosus (SLE) and may cause severe allergic reactions, even in people without a known allergy history.

Routine use of diuretics during normal pregnancy is not recommended. HCTZ passes into breast milk, so talk with your healthcare provider before using it while breastfeeding.

Contraindications

Avoid taking or using this medication if any of the following apply:

• Anuria (the kidneys are not producing urine).
• A known allergy or hypersensitivity to hydrochlorothiazide or to other sulfonamide (sulfa) medications.

Side Effects

Common side effects of HCTZ include:

• Increased urination, especially when first starting treatment
• Dizziness or lightheadedness when standing up (orthostatic hypotension)
• Weakness or fatigue
• Headache
• Nausea, vomiting, diarrhea, or stomach cramps
• Constipation or loss of appetite
• Muscle cramps or spasms
• Tingling sensations
• Sensitivity to sunlight (photosensitivity)
• Erectile dysfunction
• Transient blurred vision or yellow-tinted vision

Get medical help immediately for any signs of a serious allergic reaction such as swelling of the face, lips, tongue, or throat, trouble breathing, hives, or a severe rash.

Other serious problems can include severe skin reactions, sudden eye pain or vision changes, severe electrolyte imbalances, pancreatitis, kidney problems with reduced urine output, liver problems with yellowing of the skin or eyes, low blood counts, and lung problems.

Long-term use can also increase the risk of non-melanoma skin cancer, so any new or changing skin lesions should be checked.

References

• Hydrochlorothiazide Tablets, USP Highlights of Prescribing Information. Morgantown, WV: Mylan Pharmaceuticals Inc.; 2011.
• Hydrochlorothiazide Tablets Drug Label Information. Durham, NC: Accord Healthcare, Inc.; 2024.