This medication is used to treat edema associated with conditions such as congestive heart failure, liver cirrhosis, premenstrual tension, and various renal disorders including nephrotic syndrome, acute glomerulonephritis, and chronic renal failure. It is also indicated for the management of hypertension, either as a single therapy or in combination with other antihypertensive agents.

Thiazide diuretics, such as hydrochlorothiazide, help remove excess fluid from the body by increasing urine output. They act by inhibiting the reabsorption of sodium and chloride in the distal convoluted tubules of the kidneys. As a result, water excretion increases, along with a loss of potassium and a rise in serum uric acid levels. Although thiazides are widely used in the treatment of hypertension, their blood pressure–lowering effect is not solely due to their diuretic action. They have been shown to reduce complications and mortality related to hypertension, although the exact mechanism is not completely understood.Additionally, thiazides produce vasodilation by activating calcium-sensitive potassium channels in vascular smooth muscle and by inhibiting certain carbonic anhydrase enzymes within vascular tissues.

Edema: initially 25 to 50 mg daily, reduced for maintenance if possible; maximum 100 mg daily.

Hypertension: 25 mg daily, increased to 50 mg daily if necessary.

Elderly: in some patients, especially the elderly an initial dose of 12.5 mg daily may be sufficient.

Children: An initial dose for children has been 1 to 2 mg per kg body-weight in 2 divided doses. Infants under 6 months may need doses up to 3 mg per kg daily.

Alcohol, barbiturates, or narcotics: Taking these together may increase the risk of orthostatic hypotension (a drop in blood pressure when standing). Oral or injectable antidiabetic medications may need dose adjustments when used at the same time. Other antihypertensive drugs may produce an additive blood pressure–lowering effect. Stopping diuretic therapy 2–3 days before starting an ACE inhibitor may reduce the chance of first-dose hypotension. The antihypertensive effect may be stronger in patients who have undergone sympathectomy.

Cholestyramine and colestipol resins: These substances reduce the absorption of hydrochlorothiazide. A single dose of cholestyramine or colestipol can bind the drug and decrease its gastrointestinal absorption by up to 85% and 43%, respectively.

Corticosteroids or ACTH: May worsen thiazide-induced electrolyte loss, especially hypokalemia.

Pressor amines (e.g., adrenaline): May show reduced effectiveness in raising blood pressure when used with hydrochlorothiazide, but still remain clinically useful.

Non-depolarizing muscle relaxants (e.g., tubocurarine): May have enhanced muscle-relaxing effects when used with hydrochlorothiazide.

NSAIDs: May reduce both the diuretic and antihypertensive effects of the drug.

Drug/laboratory tests: Thiazides can affect calcium metabolism and may interfere with parathyroid function tests.

Anuria,Hypersensitivity to hydrochlorothiazide or sulfonamide-derived drugs, Severe kidney or liver failure, Addison’s disease, Hypercalcemia, Concurrent use of lithium.

Gastrointestinal system: Loss of appetite, stomach irritation, nausea, vomiting, cramps, diarrhea, constipation, jaundice (intrahepatic cholestasis), pancreatitis, inflammation of salivary glands

Central nervous system: Dizziness, vertigo, tingling sensations, headache, yellow vision

Hematological: Low white blood cells, agranulocytosis, low platelets, aplastic anemia, hemolytic anemia

Cardiovascular: Low blood pressure, including orthostatic hypotension

Hypersensitivity: Purpura, sensitivity to sunlight, rash, hives, vasculitis, fever, respiratory distress (including pneumonitis and pulmonary edema), severe allergic reactions, toxic epidermal necrolysis

Metabolic: High blood sugar, glucose in urine, high uric acid levels, electrolyte imbalance (including low sodium and low potassium)

Renal: Kidney dysfunction, interstitial nephritis, kidney failure

Other: Muscle spasms, weakness, restlessness, temporary blurred vision, impotence

If side effects become moderate or severe, the dose should be reduced or the treatment discontinued.

Use in pregnancy: Thiazides can cross the placenta and appear in cord blood. Therefore, the benefits must be carefully weighed against potential risks to the fetus. Risks may include fetal or neonatal jaundice, low platelet count, and other possible adverse effects. Routine use of diuretics in healthy pregnant women (with or without mild edema) is not recommended due to risks such as reduced blood volume, increased blood thickness, and decreased placental blood flow.

Use in breastfeeding: Thiazides are excreted in breast milk. If the drug is necessary, breastfeeding should be discontinued.

Patients should be closely observed for signs of fluid and electrolyte imbalance such as hyponatremia, hypochloremic alkalosis, hypokalemia, and hypomagnesemia. Monitoring of serum and urine electrolytes is especially important in patients experiencing excessive vomiting or receiving intravenous fluids. Common warning signs of imbalance include dry mouth, thirst, weakness, fatigue, drowsiness, restlessness, seizures, confusion, muscle pain or cramps, muscle fatigue, low blood pressure, reduced urine output, rapid heartbeat, and gastrointestinal symptoms like nausea and vomiting. Hypokalemia may occur, particularly with rapid diuresis, in patients with severe liver cirrhosis, or after prolonged treatment. It may increase the heart’s sensitivity to digitalis toxicity, leading to arrhythmias. Allergic reactions may occur in patients with or without a prior history of allergy or asthma. Hypokalemia can be prevented or treated by using potassium-sparing agents such as amiloride hydrochloride, potassium supplements, or potassium-rich foods. Diuretic-induced hyponatremia is usually mild and without symptoms. In patients with edema, especially in hot weather, dilutional hyponatremia may occur. In most cases, restricting water intake is preferred over salt administration unless the condition is severe. Thiazides may reduce serum protein-bound iodine without affecting thyroid function. They may also decrease urinary calcium excretion and occasionally cause slight increases in serum calcium levels. Thiazides should be stopped before conducting parathyroid function tests. When creatinine clearance falls below 30 ml/min, thiazide diuretics become ineffective. Uremia may develop or worsen, especially in patients with kidney impairment. If worsening uremia or reduced urine output occurs, the drug should be discontinued. Use with caution in patients with liver disease, as small changes in fluid and electrolyte balance may trigger hepatic coma. Thiazide therapy may increase uric acid levels and trigger gout. It may also impair glucose tolerance and raise cholesterol and triglyceride levels. There have been reports of worsening or activation of systemic lupus erythematosus. Latent diabetes may become apparent during treatment.

The most common symptoms of overdose are due to electrolyte imbalance (such as hypokalemia, hypochloremia, hyponatremia) and dehydration caused by excessive diuresis. If digitalis is also being used, hypokalemia may increase the risk of cardiac arrhythmias. In case of overdose, treatment should be supportive and symptomatic. If the drug was recently taken, vomiting may be induced or gastric lavage may be performed. Dehydration, electrolyte imbalance, hepatic coma, and low blood pressure should be managed using standard medical treatment. If necessary, oxygen therapy or artificial respiration should be provided in cases of respiratory distress.

Thiazide diuretics & related drugs

Keep below 30°C, Protect from light and moisture, Keep out of reach of children.