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Trade Names:
Diuril
- Tablets 250 mg
- Tablets 500 mg
- Oral suspension 250 mg/5 mL
- Powder for injection, lyophilized 500 mg (as sodium)

Trade Names:
Diurigen
- Tablets 500 mg

Mechanism of Action

Pharmacology

Enhances excretion of sodium, chloride, and water by interfering with transport of sodium ions across renal tubular epithelium.

Pharmacokinetics

Distribution

Chlorothiazide crosses the placenta but not the blood-brain barrier.

Metabolism

Chlorothiazide is not metabolized.

Elimination

Excreted by the kidney. Plasma t _½ 45 to 120 min. Following IV administration, 96% is excreted unchanged in the urine within 23 h.

Onset

Within 2 h after oral administration; within 15 min after IV administration.

Peak

Approximately 4 h after oral administration; approximately 30 min after IV administration.

Duration

Approximately 6 to 12 h after oral administration.

Indications and Usage

Adjunctive treatment in edema associated with CHF, hepatic cirrhosis, and corticosteroid and estrogen therapy; edema caused by various forms of renal function impairment such as nephrotic syndrome, acute glomerulonephritis, and chronic renal failure (oral and IV); management of hypertension (oral).

Contraindications

Anuria, hypersensitivity to sulfonamide-derived drugs or any component of this product.

Dosage and Administration

PO 30 mg/kg in 2 divided doses may be required.

PO 10 to 20 mg/kg/day in single or 2 divided doses (max, 375 mg/day).

PO 1 g/day.

PO 500 to 1,000 mg once or twice daily. Many patients respond to intermittent therapy (alternate day therapy or administration on 3 to 5 days each wk).

IV Should be reserved for patients unable to take oral medication or for emergency situations. Individualize dosage according to patient response, using the smallest dosage necessary.

PO 500 to 1,000 mg as a single or divided dose. Increase or decrease dose according to BP response. Rarely, some patients may require up to 2 g/day in divided doses.

General Advice

• Tablets and suspension
• Administer without regard to meals. Administer with food if GI upset occurs.
• Shake suspension well before measuring dose. Use dosing syringe, spoon, or cup to measure prescribed dose of suspension.

• Injection
• Reconstitute powder for injection following manufacturer's recommendations using sterile water for injection.
• Do not administer if particulate matter, cloudiness, or discoloration is noted.
• Administer by slow IV injection or IV infusion as ordered. Take special precautions to avoid extravasation.
• Discard any unused portion of vial. Do not save for future use.

Storage/Stability

Store tablets and suspension at controlled room temperature (59° to 86°F). Protect from freezing. Store powder for injection in refrigerator (36° to 46°F) or at controlled room temperature.

Drug Interactions

May potentiate orthostatic hypotension.

May reduce thiazide absorption; give thiazide at least 2 h before bile acid sequestrants.

May cause hyperglycemia.

Diuretic-induced hypokalemia and hypomagnesemia may precipitate digitalis-induced arrhythmias.

May decrease renal excretion of lithium.

Synergistic effects may result in profound diuresis and serious electrolyte abnormalities.

May decrease hypoglycemic effect of sulfonylureas. Because chlorothiazide may elevate blood glucose levels, may need to increase dosage of sulfonylureas or insulin.

Laboratory Test Interactions

May produce false-negative results with the phentolamine and tyramine tests; may interfere with the phenolsulfonphthalein test because of decreased excretion; may cause diagnostic interference of serum electrolyte levels, blood and urine glucose levels, and a decrease in serum protein-bound iodine levels without signs of thyroid disturbance.

Adverse Reactions

Cardiovascular

Hypotension; orthostatic hypotension.

CNS

Vertigo; paresthesia; dizziness; headache; restlessness.

Dermatologic

Erythema multiforme (including Stevens-Johnson syndrome); exfoliative dermatitis (including toxic epidermal necrolysis); alopecia.

EENT

Transient blurred vision; xanthopsia.

GI

Pancreatitis; diarrhea; vomiting; sialoadenitis; cramping; constipation; gastric irritation; nausea; anorexia.

Genitourinary

Impotence.

Hepatic

Jaundice (intrahepatic cholestatic).

Hematologic-Lymphatic

Aplastic anemia; agranulocytosis; leukopenia; hemolytic anemia; thrombocytopenia.

Hypersensitivity

Anaphylactic reactions; necrotizing angiitis (vasculitis and cutaneous vasculitis); respiratory distress including pneumonitis and pulmonary edema; photosensitivity; fever; urticaria; rash; purpura.

Metabolic

Hyperglycemia; glycosuria; hyperuricemia.

Musculoskeletal

Weakness; muscle spasm.

Renal

Renal failure; renal dysfunction; interstitial nephritis.

Precautions

Pregnancy

Category C .

Lactation

Excreted in breast milk.

Children

Safety and efficacy not established. Oral dosing recommendation is supported by empiric use in children and published literature regarding the treatment of hypertension.

Hypersensitivity

May occur in patients with or without history of allergy or bronchial asthma; cross-sensitivity with sulfonamides also may occur.

Renal Function

Drug may precipitate azotemia; use drug with caution.

Hepatic Function

Minor alterations of fluid and electrolyte balance may precipitate hepatic coma; use with caution.

Diabetes mellitus

May become manifest.

Electrolytes

Increased urinary excretion of sodium, potassium, or magnesium may occur; decreased urinary excretion of calcium may occur.

Hyperuricemia

May occur or frank gout may be precipitated.

Lupus erythematosus

Exacerbation or activation may occur.

Postsympathectomy patients

Antihypertensive effects may be enhanced.

Overdosage

Symptoms

Electrolyte depletion (hypokalemia, hypochloremia, hyponatremia), dehydration; hypokalemia may accentuate cardiac arrhythmias if digitalis is being administered.

Patient Information

• Injection
• Advise patient that medication will be prepared by a health care professional and administered in a health care setting.

• Tablets and Suspension
• Advise patient to take prescribed dose once or twice daily without regard to meals but to take with food if stomach upset occurs.
• Advise patient or caregiver using suspension to shake well before measuring dose and to use dosing spoon, syringe, or cup to measure prescribed dose.
• Advise patient that medication will initially increase urination, but that this should go away after a few weeks of treatment.
• Advise patient if a dose is missed to skip that dose and take the next dose at the regularly scheduled time. Caution patient not to double the dose to catch up.
• Inform patient that drug controls but does not cure hypertension and to continue taking medication as prescribed even when BP is not elevated.
• Caution patient not to change the dose or stop taking unless advised by health care provider.
• Instruct patient to continue taking other BP medications as prescribed by health care provider.
• Instruct patient in BP and pulse measurement skills.
• Advise patient to monitor and record BP and pulse at home and to inform health care provider should abnormal measurements be noted. Also advise patient to take record of BP and pulse to each follow-up visit.
• Instruct patient to lie or sit down if experiencing dizziness or lightheadedness when standing.
• Caution patient that inadequate fluid intake, excessive perspiration, diarrhea, or vomiting can lead to excessive fall in BP, resulting in lightheadedness or fainting.
• Instruct patients with diabetes to monitor blood glucose more frequently when drug is started or dose is changed and to inform health care provider of significant changes in readings.
• Caution patient to avoid unnecessary exposure to UV light (eg, sunlight, tanning booths) and to use sunscreen and wear protective clothing when exposed to UV light until tolerance is determined.
• Emphasize to hypertensive patient importance of the following modalities on BP: weight control, regular exercise, smoking cessation, moderate intake of alcohol and salt.
• Instruct patient to inform health care provider if any of the following occur: muscle pain, weakness, or cramps; persistent nausea or vomiting; excessive thirst; unexplained tiredness; drowsiness; increased heart rate; unexplained joint pain; abnormal skin sensations.