HYDROCHLOROTHIAZIDE (Microzide): What is used for?

What is Hydrochlorothiazide?

Hydrochlorothiazide (HCTZ) is an active ingredient used for the treatment of High Blood Pressure, Edema, Diabetes insipidus and Nephrocalcinosis.

The brand names of Hydrochlorothiazide (HCTZ) in the United States are: HydroDIURIL, Microzide, Oretic, Esidrix.

Mechanism of action (MOA) of Hydrochlorothiazide

Inhibits the Na + Cl transport system – in the renal distal tubule, decreasing the reabsorption of Na + and increasing its excretion.

Therapeutic indications, uses and benefits of Hydrochlorothiazide (HCTZ)

– High Blood Pressure (HBP), as monotherapy or in combination with other antihypertensive agents.

– Edema of specific origin: Edema due to mild grade stable chronic heart failure to moderate (New York Heart Association, NYHA, classes II and III). Edema due to renal failure. Ascites due to liver cirrhosis in stable low patients close medical control.

– Prevention of recurrent calcium oxalate stones in patients with idiopathic, normocalcemic hypercalciuria.

– Nephrogenic diabetes insipidus when treatment with antidiuretic hormone is not indicated.

Dosage of Hydrochlorothiazide


– High blood pressure:

Adults: initial 12.5-25 mg/day; max. 50 mg/day (1 or 2 doses). If with doses of 25 mg or 50 mg/day, the decrease in pressure is inadequate, combine with other antihypertensives. Correct volume or sodium depletion before using hydrochlorothiazide in combination with an ACE inhibitor or angiotensin receptor blocker or a direct renin inhibitor.

Children: 1-2 mg/kg/day (single dose or 2 doses); max. 3 mg/kg/day.

Infants < 6 months: max. 3 mg/kg/day.

– Edema of specific origin:

Adults: 25-100 mg/day (1 or 2 intakes), others respond to intermittent tto. (dose on alternate days, from 3 to 5 days/week).

Children: 2 mg/kg/day (in 2 times); max. 3 mg/kg/day.

Infants < 6 months: max. 3 mg/kg/day.

In premenstrual syndrome: limit to those showing weight gain > 1.4 kg.

– Nephrogenic diabetes insipidus:

Adults: 50-100 mg/day.

Children: to be determined individually and in hospital (little experience).

– Prophylaxis of recurrent calcium oxalate stones in normocalcemic hypercalciuria:

Adults: recommended dose: 25-50 mg/day

Mode of administration of Hydrochlorothiazide (HCTZ)

Oral use.
The tablets can be taken whole, broken or crushed, with the help of a little water or another non-alcoholic drink. S
It can be given daily as a single dose or in two divided doses. It can be taken with or without food.

Contraindications of Hydrochlorothiazide (HCTZ)

  • Hypersensitivity to hydrochlorothiazide (thiazides in general).
  • Anuria.
  • Electrolytic depletion.
  • Decompensated diabetes.
  • Addison’s disease.
  • Pregnancy.
  • Breastfeeding.

Warnings and precautions with Hydrochlorothiazide

  • Elderly (greater sensitivity).
  • Severe renal failure.
  • Severe liver failure (hypovolemia produced triggers azotemia).
  • Diabetics (impairs glucose tolerance).
  • Gout or hyperuricemia.
  • History of pancreatitis.
  • May cause electrolyte imbalance (hypercalcemia, hypokalemia, hyponatremia, hypomagnesemia).
  • Increases in cholesterol levels and triglycerides.
  • Serum electrolyte control.
  • Risk of sensitivity reactions with and without a history of allergy or bronchial asthma.
  • Exacerba or active systemic lupus erythematosus.
  • Additive effects with other diuretics or antihypertensives.
  • Acute myopia and closed-angle secondary glaucoma.
  • Continued long-term use with hydrochlorothiazide may increase the risk of non-melanocytic skin cancer.
  • It is recommended: to reconsider the use of hydrochlorothiazide with a history of non-melanocytic skin cancer and to monitor the presence of skin alterations in prolonged treatments with hydrochlorothiazide.

Liver failure 

An adjustment of the initial dose is not necessary in patients with medium to moderate liver failure.
Thiazides, like other diuretics, can produce an electrolyte imbalance, hepatic encephalopathy, and hepato-renal syndrome when used to treat cirrhotic ascites.

Hydrochlorothiazide should be used with particular caution in patients with severe liver failure.

Kidney failure

An adjustment of the initial dose is not necessary in patients with mild to moderate renal failure.
Use with caution in patients with severe kidney disease (IFG<30 ml/min).

Hydrochlorothiazide and other thiazide diuretics may lose their diuretic effect when IFG is < 30 ml/min but may be useful in these patients when used with caution in combination with loop diuretics.
Hydrochlorothiazide is contraindicated in patients with anuria.

Interactions with Hydrochlorothiazide (HCTZ)

  • Antihypertensive effect increased by: baclofen, other antihypertensive.
  • Mutual toxicity potentiation with: ACEi, ß-blockers (hyperglycemia), carbamazepine, allopurinol (allergies).
  • Decreased absorption by: cholestyramine, colestipol.
  • Intensified hypokalemia by: corticosteroids, ACTH, parenteral amphotericin B, carbenoxolone, stimulant laxatives.
  • Risk of: hypercalcemia with Ca salts, hyperuricemia with cyclosporine.
  • Risk of increased urea from: tetracyclines.
  • Diminishes effect of: pressor amines.
  • Increases effect of: myorelaxatives not depolarizing.
  • Adjust dose of: antigotosos, antidiabetic.
  • Effect decreased by: indomethacin.
  • Increases adverse effects of: digitalis, lithium, amantadine.
  • Caution with: drugs that produce “torsades de pointes” (for hypokalemia).
  • Increased bioavailability with: anticholinergic agents (due to decreased gastrointestinal motility and speed of emptying the stomach).
  • Risk of hemolytic anemia with: methyldopa (isolated cases).
  • Reduces renal excretion of: cytotoxic agents. (cyclophosphamide, methotrexate).
  • Orthostatic hypotension potency with: alcohol, barbiturates, narcotics or antidepressants.
  • Increases photosensitizing effects of: griseofulvin, phenothiazines, sulfonamides and sulfonylureas, tetracyclines, retinoids and agents in photodynamic therapy.
  • Lab: interferes with parathyroid function tests.

Pregnancy and Hydrochlorothiazide

Thiazides go through the placenta. Regular use of diuretics exposes the mother and fetus to fetal or neonatal jaundice, thrombocytopenia.


Hydrochlorothiazide is excreted by milk and may inhibit lactation. It is contraindicated during lactation due to the possibility of adverse effects in the infant.

Effects on driving ability

Hydrochlorothiazide can cause dizziness, headache and vertigo, so the ability to drive and use machines can be altered, mainly at the beginning of treatment, or when dosage is modified and also in combination with alcohol intake, but these effects depend on individual susceptibility. If you experience dizziness, headache or dizziness, you should avoid these activities.

Adverse reactions and side effects of Hydrochlorothiazide (HCTZ)

Adverse effects are rare (<10%) and generally dose-related, and can be minimized by establishing the minimum effective dose, particularly in high blood pressure.


Source: The content of this active ingredient has been written taking into account the clinical and molecular information of all medicines authorised and marketed in the United States under the Unique Ingredient Identifier (UNII) by the Substance Registration System (SRS) of the Food and Drug Administration (FDA) and the United States Pharmacopeia (USP).

In order to know in detail the information authorized by the FDA for each drug, you should consult the corresponding medication guide authorized by the FDA.


PubChem CID: 3639
NCI Thesaurus: C29098


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