Hydrochlorothiazide (Microzide): Uses, Warnings & More
Quick summary: Hydrochlorothiazide (HCTZ) is a thiazide diuretic used for conditions such as high blood pressure and certain types of edema. It is also listed for some other specific uses in official product information....
This content is for educational purposes only and does not replace medical advice, diagnosis or treatment from a qualified healthcare professional.
Quick summary: Hydrochlorothiazide (HCTZ) is a thiazide diuretic used for conditions such as high blood pressure and certain types of edema. It is also listed for some other specific uses in official product information. Always check the exact leaflet for the brand and strength prescribed.
Brand names mentioned in the U.S.: HydroDIURIL, Microzide, Oretic, Esidrix.
Medical disclaimer: This article is for general information only and does not replace advice from a doctor, pharmacist, or the official FDA medication guide. Do not use it to self-diagnose, and do not start, stop, or change any medicine without professional guidance.
What is hydrochlorothiazide?
Hydrochlorothiazide (HCTZ) is an active ingredient used in medicine. It is a thiazide diuretic, which means it helps the body remove extra salt and water through the kidneys.
According to the source content, hydrochlorothiazide is used for high blood pressure, edema, diabetes insipidus, and nephrocalcinosis. It is also listed for prevention of recurrent calcium oxalate stones in selected patients.
How hydrochlorothiazide works
Hydrochlorothiazide inhibits the Na+ / Cl- transport system in the renal distal tubule. This reduces sodium reabsorption and increases sodium excretion.
In practical terms, this diuretic action can help lower fluid buildup and support blood pressure control.
What hydrochlorothiazide is used for
The source content lists the following therapeutic uses:
- High blood pressure, alone or with other antihypertensive medicines.
- Edema of specific origin, including edema related to stable chronic heart failure, renal failure, and ascites due to liver cirrhosis under close medical supervision.
- Prevention of recurrent calcium oxalate stones in patients with idiopathic, normocalcemic hypercalciuria.
- Nephrogenic diabetes insipidus when antidiuretic hormone treatment is not indicated.
How it is taken
Hydrochlorothiazide is taken by mouth. The tablets may be taken whole, broken, or crushed with a little water or another non-alcoholic drink.
It may be taken with or without food, and it can be given as a single daily dose or in divided doses, depending on the prescribed regimen.
Dosage information from the source
The following dose ranges were included in the original content. These are general reference points only and should be verified in the official leaflet and by a healthcare professional.
| Use | Adults | Children / infants |
|---|---|---|
| High blood pressure | Initial 12.5–25 mg/day; maximum 50 mg/day | 1–2 mg/kg/day; maximum 3 mg/kg/day |
| Edema of specific origin | 25–100 mg/day | 2 mg/kg/day; maximum 3 mg/kg/day |
| Nephrogenic diabetes insipidus | 50–100 mg/day | To be determined individually in hospital |
| Prevention of recurrent calcium oxalate stones | 25–50 mg/day | Not listed in the source content |
Important: The original content also notes that if blood pressure reduction is not adequate at 25 mg/day or 50 mg/day, hydrochlorothiazide may be combined with other antihypertensive medicines under medical supervision.
Contraindications listed in the source
- Hypersensitivity to hydrochlorothiazide or thiazides in general.
- Anuria.
- Electrolyte depletion.
- Decompensated diabetes.
- Addison’s disease.
- Pregnancy.
- Breastfeeding.
Warnings and precautions
The source content highlights several situations where extra caution is needed:
- Older adults, who may be more sensitive.
- Severe kidney failure.
- Severe liver failure.
- Diabetes, because glucose tolerance may be affected.
- Gout or hyperuricemia.
- History of pancreatitis.
- Possible electrolyte imbalance, including changes in calcium, potassium, sodium, and magnesium.
- Possible increases in cholesterol and triglycerides.
- Risk of sensitivity reactions, even without a prior allergy or asthma history.
- Systemic lupus erythematosus may worsen or become active.
- Possible additive effects with other diuretics or antihypertensive medicines.
- Possible acute myopia and secondary angle-closure glaucoma.
- Long-term use may increase the risk of non-melanoma skin cancer.
If you have a history of skin cancer or notice skin changes during prolonged treatment, the source recommends reviewing this with a clinician.
Liver and kidney considerations
Liver failure
The source states that an initial dose adjustment is not necessary in mild to moderate liver failure. However, hydrochlorothiazide should be used with particular caution in severe liver failure.
It also notes that thiazides can contribute to electrolyte imbalance, hepatic encephalopathy, and hepatorenal syndrome when used for cirrhotic ascites.
Kidney failure
The source states that an initial dose adjustment is not necessary in mild to moderate renal failure. It should be used with caution in severe kidney disease.
Thiazides may lose diuretic effect when kidney function is very low, although they may still be used cautiously with loop diuretics in some cases under medical supervision. Hydrochlorothiazide is contraindicated in anuria.
Interactions listed in the source
Hydrochlorothiazide may interact with many medicines. The original content lists the following examples:
- Other antihypertensives and baclofen may increase the blood pressure-lowering effect.
- ACE inhibitors, beta-blockers, carbamazepine, and allopurinol may increase certain risks or toxicity.
- Cholestyramine and colestipol may reduce absorption.
- Corticosteroids, ACTH, amphotericin B, carbenoxolone, and stimulant laxatives may worsen hypokalemia.
- Calcium salts may increase hypercalcemia risk.
- Cyclosporine may increase hyperuricemia risk.
- Tetracyclines may increase urea.
- Pressor amines may have reduced effect.
- Non-depolarizing muscle relaxants may have increased effect.
- Antigout and antidiabetic medicines may need dose review by a clinician.
- Indomethacin may reduce effect.
- Digitalis, lithium, and amantadine may have increased adverse effects.
- Medicines associated with torsades de pointes require caution because of possible hypokalemia.
- Anticholinergic agents may increase bioavailability.
- Methyldopa has been linked to isolated cases of hemolytic anemia.
- Cytotoxic agents such as cyclophosphamide and methotrexate may have reduced renal excretion.
- Alcohol, barbiturates, narcotics, and antidepressants may increase orthostatic hypotension.
- Several photosensitizing medicines may increase light sensitivity.
- It may interfere with parathyroid function tests.
If you take any regular medicine, the safest step is to compare it with the official leaflet or ask a pharmacist to check for interactions.
Pregnancy and breastfeeding
The source content states that thiazides cross the placenta and that regular use of diuretics may expose the mother and fetus to fetal or neonatal jaundice and thrombocytopenia.
It also states that hydrochlorothiazide is excreted in breast milk and may inhibit lactation, so it is contraindicated during breastfeeding in the source material.
Driving and using machines
Hydrochlorothiazide can cause dizziness, headache, and vertigo. These effects may be more noticeable at the start of treatment, after a dose change, or when combined with alcohol.
If you feel unwell or dizzy, avoid driving or using machinery until you are fully alert.
Side effects
The original content says adverse effects are generally rare and dose-related, and that they may be minimized by using the minimum effective dose, especially for high blood pressure.
Because side effects can vary, it is important to review the official patient leaflet and speak with a healthcare professional if you notice new or worsening symptoms.
Safety reminder
Do not use this article to decide whether hydrochlorothiazide is right for you. If you have kidney disease, liver disease, diabetes, gout, pregnancy, breastfeeding, or take other medicines, ask a doctor or pharmacist to review the official product information first.
Frequently asked questions
▸ What is hydrochlorothiazide mainly used for?
The source content lists high blood pressure and certain types of edema as the main uses. It also includes some other specific indications such as prevention of recurrent calcium oxalate stones and nephrogenic diabetes insipidus.
▸ Is hydrochlorothiazide a diuretic?
Yes. It is a thiazide diuretic, which means it helps the body remove extra salt and water through the kidneys.
▸ Can hydrochlorothiazide be taken with food?
The source content says it can be taken with or without food.
▸ What should I check before taking it?
Check the official leaflet and confirm any kidney, liver, pregnancy, breastfeeding, diabetes, gout, or interaction concerns with a healthcare professional.
▸ Can it affect driving?
Yes. The source content warns that dizziness, headache, and vertigo may affect driving or machine use, especially early in treatment or after dose changes.
▸ Where can I verify official information?
The FDA medication guide and the product’s official leaflet are the best places to verify approved uses, warnings, and instructions.
Official sources and references
The original content points readers to FDA and drug-information resources for verification of the active ingredient and official product information.
- FDA Medication Guides
- UNII: 0J48LPH2TH
- ChemIDplus
- DrugPortal
- PubChem CID: 3639
- NCI Thesaurus: C29098
Medical disclaimer
This content is for educational purposes only. It should not be used as a substitute for professional medical advice, diagnosis or treatment. Always ask a doctor, pharmacist or qualified healthcare professional before starting, stopping or changing any medicine.
Sources and verification
The following sources or official references are listed to support verification of the medicine information discussed in this article.
Medicine information can change and may vary depending on country, product formulation, patient history and professional guidance. Always check official medicine information and ask a healthcare professional for personal medical questions.