Chlorothiazide

Chlorothiazide

Usual Diluents

Standard Dilutions   [Amount of drug] [Infusion volume] [Infusion rate]

May also be administered SLOWLY by direct intravenous injection over at least 5 minutes.

Extravasation must be rigidly avoided. Do not give subcutaneously or intramuscularly. The pH of the reconstituted solution is >9.0

IV administration should be reserved for patients who are unable to take the drug orally.

Reconstitution:
Add 18 mL of Sterile Water for Injection to the vial to form an isotonic solution for intravenous injection. Never add less than 18 mL. When reconstituted with 18 mL of Sterile Water, the final concentration of intravenous chlorothiazide sodium is 28 mg/mL.

Stability: Generally, the reconstituted solution should be used immediately after reconstitution.  Some references suggest stability intervals up to but not exceeding 24 hours. [CONSIDER THE ADMIXTURE A SHORT-STABILITY PREPARATION - INFUSION SHOULD OCCUR <6-12 HRS AFTER PREPARATION]

Stability / Miscellaneous

Chlorothiazide affects the distal renal tubular mechanism of electrolyte reabsorption. At maximal therapeutic dosage all thiazides are approximately equal in their diuretic efficacy.

Chlorothiazide increases excretion of sodium and chloride in approximately equivalent amounts. Natriuresis may be accompanied by some loss of potassium and bicarbonate.

After oral use diuresis begins within 2 hours, peaks in about 4 hours and lasts about 6 to 12 hours. Following intravenous use of chlorothiazide sodium, onset of the diuretic action occurs in 15 minutes and the maximal action in 30 minutes.

Pharmacokinetics and Metabolism
Chlorothiazide is not metabolized but is eliminated rapidly by the kidney; 96 percent of an intravenous dose is excreted unchanged in the urine within 23 hours. The plasma half-life of chlorothiazide is 45 to 120 minutes. Chlorothiazide crosses the placental but not the blood-brain barrier and is excreted in breast milk.

INDICATIONS AND USAGE
Chlorothiazide sodium for injection is indicated as adjunctive therapy in edema associated with congestive heart failure, hepatic cirrhosis, and corticosteroid and estrogen therapy.

Chlorothiazide sodium for injection has also been found useful in edema due to various forms of renal dysfunction such as nephrotic syndrome, acute glomerulonephritis, and chronic renal failure.

CONTRAINDICATIONS
Anuria. Hypersensitivity to any component of this product or to other sulfonamide-derived drugs.

PRECAUTIONS
General
All patients receiving diuretic therapy should be observed for evidence of fluid or electrolyte imbalance: namely, hyponatremia, hypochloremic alkalosis, and hypokalemia. Serum and urine electrolyte determinations are particularly important when the patient is vomiting excessively or receiving parenteral fluids. Warning signs or symptoms of fluid and electrolyte imbalance, irrespective of cause, include dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, confusion, seizures, muscle pains or cramps, muscular fatigue, hypotension, oliguria, tachycardia, and gastrointestinal disturbances such as nausea and vomiting.

Hypokalemia may develop especially with brisk diuresis, when severe cirrhosis is present or after prolonged therapy.

Interference with adequate oral electrolyte intake will also contribute to hypokalemia. Hypokalemia may cause cardiac arrhythmias and may also sensitize or exaggerate the response of the heart to the toxic effects of digitalis (e.g., increased ventricular irritability). Hypokalemia may be avoided or treated by use of potassium- sparing diuretics or potassium supplements such as foods with a high potassium content.

Although any chloride deficit is generally mild and usually does not require specific treatment except under extraordinary circumstances (as in liver disease or renal disease), chloride replacement may be required in the treatment of metabolic alkalosis.

Dilutional hyponatremia may occur in edematous patients in hot weather; appropriate therapy is water restriction, rather than administration of salt, except in rare instances when the hyponatremia is life-threatening. In actual salt depletion, appropriate replacement is the therapy of choice.

Hyperuricemia may occur or acute gout may be precipitated in certain patients receiving thiazides.

In diabetic patients dosage adjustments of insulin or oral hypoglycemic agents may be required.

Hyperglycemia may occur with thiazide diuretics. Thus latent diabetes mellitus may become manifest during thiazide therapy.

The antihypertensive effects of the drug may be enhanced in the postsympathectomy patient.

If progressive renal impairment becomes evident, consider withholding or discontinuing diuretic therapy.

Thiazides have been shown to increase the urinary excretion of magnesium; this may result in hypomagnesemia.

Thiazides may decrease urinary calcium excretion. Thiazides may cause intermittent and slight elevation of serum calcium in the absence of known disorders of calcium metabolism. Marked hypercalcemia may be evidence of hidden hyperparathyroidism. Thiazides should be discontinued before carrying out tests for parathyroid function.

Increases in cholesterol and triglyceride levels may be associated with thiazide diuretic therapy.

Laboratory Tests

Periodic determination of serum electrolytes to detect possible electrolyte imbalance should be done at appropriate intervals.

Drug Interactions
When given concurrently the following drugs may interact with thiazide diuretics.

Alcohol, barbiturates, or narcotics - potentiation of orthostatic hypotension may occur.

Antidiabetic drugs - (oral agents and insulin) - dosage adjustment of the antidiabetic drug may be required.

Other antihypertensive drugs - additive effect or potentiation.

Corticosteroids, ACTH - intensified electrolyte depletion, particularly hypokalemia.

Pressor amines (e.g., norepinephrine) - possible decreased response to pressor amines but not sufficient to preclude their use.

Skeletal muscle relaxants, nondepolarizing (e.g., tubocurarine) - possible increased responsiveness to the muscle relaxant.

Lithium - generally should not be given with diuretics. Diuretic agents reduce the renal clearance of lithium and add a high risk of lithium toxicity. Refer to the package insert for lithium preparations before use of such preparations with chlorothiazide sodium.

Non-steroidal Anti-inflammatory Drugs - In some patients, the administration of a non-steroidal anti-inflammatory agent can reduce the diuretic, natriuretic, and antihypertensive effects of loop, potassium-sparing and thiazide diuretics. Therefore, when chlorothiazide sodium and non-steroidal anti-inflammatory agents are used concomitantly, the patient should be observed closely to determine if the desired effect of the diuretic is obtained.

DOSAGE AND ADMINISTRATION
Chlorothiazide sodium for injection should be reserved for patients unable to take oral medication or for emergency situations.

Therapy should be individualized according to patient response. Use the smallest dosage necessary to achieve the required response.

Intravenous use in infants and children has been limited and is not generally recommended.

When medication can be taken orally, therapy with chlorothiazide tablets or oral suspension may be substituted for intravenous therapy, using the same dosage schedule as for the parenteral route.

Chlorothiazide sodium for injection may be given slowly by direct intravenous injection or by intravenous infusion.

Extravasation must be rigidly avoided. Do not give subcutaneously or intramuscularly.

The usual adult dosage is 500 mg to 1 g once or twice a day. Many patients with edema respond to intermittent therapy, i.e., administration on alternate days or on three to five days each week. With an intermittent schedule, excessive response and the resulting undesirable electrolyte imbalance are less likely to occur.

Directions for Reconstitution
Use aseptic technique. Because chlorothiazide sodium for injection contains no preservative, a fresh solution should be prepared immediately prior to each administration, and the unused portion should be discarded.

Add 18 mL of Sterile Water for Injection to the vial to form an isotonic solution for intravenous injection. Never add less than 18 mL. When reconstituted with 18 mL of Sterile Water, the final concentration of intravenous chlorothiazide sodium is 28 mg/mL. The reconstituted solution is clear and essentially free from visible particles. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to use whenever solution and container permit. The solution is compatible with dextrose or sodium chloride solutions for intravenous infusion. Avoid simultaneous administration of solutions of chlorothiazide with whole blood or its derivatives.

HOW SUPPLIED
Chlorothiazide Sodium for Injection, USP is a dry, sterile lyophilized powder, supplied as follows:
500 mg/vial - Packaged individually.
Vial stoppers do not contain natural rubber latex.

Storage
Store lyophilized powder between 2 and 25°C (36 and 77°F).

For single dose only. Use solution immediately after reconstitution. Discard unused portion of the reconstituted solution.

Source: [package insert]