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Apo-Chlorthalidone (CA), Hygroton (UK), Novo-Thalidone (CA), Thalitone, Uridon (CA)

Pharmacologic class: Thiazide-like diuretic

Therapeutic class: Diuretic, antihypertensive

Pregnancy risk category B


Unclear. Enhances excretion of sodium, chloride, and water by interfering with transport of sodium ions across renal tubular epithelium. Also may dilate arterioles.


Tablets: 15 mg, 25 mg, 50 mg, 100 mg

Indications and dosages

Edema associated with heart failure, renal dysfunction, cirrhosis, corticosteroid therapy, and estrogen therapy

Adults: 50 to 100 mg/day (30 to 60 mg Thalitone) P.O. or 100 mg every other day (60 mg Thalitone) P.O., up to 200 mg/day (120 mg Thalitone) P.O.

Management of mild to moderate hypertension

Adults: 25 mg/day (15 mg Thalitone) P.O. Based on patient response, may increase to 50 mg/day (30 to 50 mg Thalitone) P.O., then up to 100 mg/day (except Thalitone) P.O.


• Hypersensitivity to drug, other thiazides, sulfonamides, or tartrazine

• Renal decompensation


Use cautiously in:

• renal or severe hepatic disease, abnormal glucose tolerance, gout, systemic lupus erythematosus, hyperparathyroidism, bipolar disorder

• elderly patients

• pregnant or breastfeeding patients.


• Know that dosages above 25 mg/day are likely to increase potassium excretion without further increasing sodium excretion or reducing blood pressure.

Adverse reactions

CNS: dizziness, vertigo, drowsiness, lethargy, confusion, headache, insomnia, nervousness, paresthesia, asterixis, nystagmus, encephalopathy

CV: hypotension, ECG changes, chest pain, arrhythmias, thrombophlebitis

GI: nausea, vomiting, cramping, anorexia, pancreatitis

GU: polyuria, nocturia, erectile dysfunction, loss of libido

Hematologic: blood dyscrasias

Metabolic: gout attack, dehydration, hyperglycemia, hypokalemia, hypocalcemia, hypomagnesemia, hyponatremia, hypophosphatemia, hyperuricemia, hyperlipidemia,

hypochloremic alkalosis

Musculoskeletal: muscle cramps, muscle spasms

Skin: flushing, photosensitivity, hives, rash, exfoliative dermatitis, toxic epidermal necrolysis

Other: fever, weight loss, hypersensitivity reactions


Drug-drug. Allopurinol: increased risk of hypersensitivity reaction

Amphotericin B, corticosteroids, mezlocillin, piperacillin, ticarcillin: additive hypokalemia

Antihypertensives, barbiturates, nitrates, opiates: increased hypotension

Cholestyramine, colestipol: decreased chlorthalidone blood level

Digoxin: increased risk of hypokalemia

Lithium: increased risk of lithium toxicity

Nonsteroidal anti-inflammatory drugs: decreased diuretic effect

Drug-diagnostic tests. Bilirubin, calcium, creatinine, uric acid: increased levels

Glucose (in diabetic patients): increased blood and urine levels

Magnesium, potassium, protein-bound iodine, sodium, urine calcium: decreased levels

Drug-herbs. Ginkgo: decreased antihypertensive effects

Licorice, stimulant laxative herbs (aloe, cascara sagrada, senna): increased risk of potassium depletion

Drug-behaviors. Acute alcohol ingestion: additive hypotension

Sun exposure: increased risk of photosensitivity

Patient monitoring

• Closely monitor patient with renal insufficiency.

• Assess for signs and symptoms of hematologic disorders.

• Monitor CBC with white cell differential and serum uric acid and electrolyte levels.

• Assess for signs and symptoms of hypersensitivity reactions, especially dermatitis.

• Watch for fluid and electrolyte imbalances.

Patient teaching

• Instruct patient to consume a low-sodium diet containing plenty of potassium-rich foods and beverages (such as bananas, green leafy vegetables, and citrus juice).

• Caution patient to avoid driving and other hazardous activities until he knows whether drug makes him dizzy or affects concentration and alertness.

• Tell patient with diabetes to check urine or blood glucose level frequently.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.


/chlor·thal·i·done/ (klor-thal´ĭ-dōn) a sulfonamide with similar actions to the thiazide diuretics; used in the treament of hypertension and edema.


A diuretic that inhibits the reabsorption of sodium and chloride by the kidneys, used to treat hypertension.


a diuretic and antihypertensive; a sulfonamide derivative.
indications It is prescribed in the treatment of high blood pressure and edema.
contraindications Anuria or known hypersensitivity to this drug, to other thiazide medication, or to sulfonamide derivatives prohibits its use.
adverse effects Among the more serious adverse reactions are hypokalemia, hyperglycemia, hyperuricemia, and hypersensitivity reactions.


Chlortalidone, a DIURETIC drug of medium potency that increases the output of urine over a period of 48 hours. Brand names are Hygroton, Kalspare, and with ATENOLOL, Tenoretic.


n brand names: Novothalidone, Apo-Chlorthalidone, Thalitone;
drug class: diuretic with thiazide-like effects;
action: acts on distal tubule by increasing excretion of water, sodium, chloride, potassium;
uses: edema, hypertension, diuresis, chronic heart disease.