Hydrochlorothiazide (Efficacy)

Hydrochlorothiazide (HCT) is a classic thiazide diuretic, which acts by inhibiting the sodium and chloride transport system in the renal distal tubule, decreasing the reabsorption of sodium and increasing its excretion. It is the most prescribed diuretic agent in patients with primary hypertension in Europe and America.


HCT is contraindicated in the following cases: Hypersensitivity to hydrochlorothiazide, anuria, liver failure and severe renal insufficiency, electrolyte depletion (hyponatremia or hypokalemia refractory to treatment), decompensated diabetes, Addison's disease, pregnancy and lactation.


Elderly patients have greater sensitivity, with greater additive effect with other diuretics or antihypertensives.

Caution should be exercised when prescribing HCT in patients with hepatic insufficiency, with renal failure ( the produced hypovolemia triggers in azotemia), in diabetic patients, in patients with gout or hyperuricemia and in patients with pancreatitis.

There is a risk of sensitivity reactions with and without a history of bronchial asthma, in addition to being able to exacerbate systemic lupus erythematosus.


Uncommon and dose-related side effects, especially side effects related to the increase in blood pressure.


The antihypertensive effect of HCT is increased by the concomitant use of baclofen and other antihypertensive drugs.

Potentiation of mutual toxicity with: ACE inhibitors (angiotensin converting enzyme inhibitors), β-blockers (hyperglycemia), carbamazepine, allopurinol (allergies).

The absorption of HCT is diminished by cholestyramine and colestipol.

Hypokalemia caused by hydrochlorothiazide can be intensified by the concomitant use of: corticosteroids, ACTH, parenteral amphotericin B, carbenoxolone and stimulant laxatives.

There is a risk of hypercalcemia in the concomitant use of HCT together with Ca salts, hyperuricemia with cyclosporine, and an increase in urea due to the use of tetracyclines.

HCT can affect the dose of other drugs: it decreases the effect of pressor amines and increases the effect of non-depolarizing muscle relaxants.

In turn, its own effect may be diminished by indomethacin and increased bioavailability with anticholinergic agents.

If you are taking HCT, the dose of antidiabetics and drugs used in the treatment of gout must be adjusted.

HCT increases the adverse effects of: digitalis, lithium, amantadine.

Caution should be exercised in the use of HCT along with drugs that produce ""Torsades de Pointes"" (attention to hypokalemia).

Concomitant use with methyldopa in isolated cases increases the risk of hemolytic anemia.

It must be remembered that HCT reduces the renal excretion of cytotoxic agents (such as cyclophosphamide and methotrexate) and that orthostatic hypotension is potentiated if alcohol, barbiturates, narcotics or antidepressants are ingested.

Hydrochlorothiazide increases the photosensitizing effects of: griseofulvin, phenothiazines, sulfonamides and sulfonylureas, tetracyclines, retinoids and agents in photodynamic therapy


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