Chlorothiazide

Chlorothiazide is a thiazide diuretic that promotes renal sodium and water excretion. Its veterinary use is less common than that of loop diuretics, but it has been used for edema and selected disorders requiring a thiazide effect. A traditional large-animal application is reduction of postpartum udder edema in dairy cattle.

Group

Thiazide diuretic

Mechanism of Action

Chlorothiazide inhibits the sodium–chloride cotransporter on the luminal surface of the distal convoluted tubule. Reduced sodium and chloride reabsorption increases their urinary loss, with accompanying water excretion and a reduction in extracellular fluid volume. The distal site of action produces a more modest diuresis than loop-diuretic blockade. In diabetes insipidus, mild volume contraction can paradoxically reduce urine output by increasing proximal fluid reabsorption.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Diuresis and hypercalciuria	20–40 mg/kg	PO	Every 12 h
Nephrogenic diabetes insipidus	20–40 mg/kg	PO	Every 12 h	Empirical adjunct; monitor water balance and electrolytes.
Systemic hypertension	20–40 mg/kg	PO	Every 12–24 h	With an appropriate dietary sodium plan.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Diuresis and hypercalciuria	20–40 mg/kg	PO	Every 12 h
Nephrogenic diabetes insipidus	20–40 mg/kg	PO	Every 12 h	Empirical adjunct; monitor water balance and electrolytes.

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Postpartum udder edema	2000 mg/animal	PO	Every 12–24 h	Oral chlorothiazide bolus; distinguish from the hydrochlorothiazide injection described elsewhere.
Injectable treatment of udder edema	Reference only	IV		The passage lists 125–250 mg IV or IM once or twice daily, but the associated cattle injectable product is hydrochlorothiazide. Drug identity is inconsistent; do not calculate this as chlorothiazide.
Diuresis	4–8 mg/kg	PO	Every 12–24 h	Adult cattle only; oral chlorothiazide.

Indications

Treatment of edema or fluid retention in selected veterinary patients requiring a thiazide diuretic.
Reduction of postpartum udder edema in dairy cattle.
Adjunctive management of nephrogenic diabetes insipidus to reduce polyuria, based on thiazide-class use and limited chlorothiazide-specific veterinary evidence.
Historically, treatment of hypercalciuria or prevention of recurrent calcium-containing uroliths in dogs; chlorothiazide-specific evidence is limited and less consistent than for hydrochlorothiazide.

Contraindications

Hypercalcemia or substantial hypercalcemia risk.
Anuria or hypersensitivity to thiazides/sulfonamides.
Use cautiously with dehydration, major electrolyte disturbance, severe renal disease, hepatic impairment or diabetes.

Interactions

Calcium and vitamin D supplementation can worsen hypercalcemia.
Amphotericin B, corticosteroids or corticotropin can intensify hypokalemia; electrolyte changes increase digoxin toxicity.
Lithium exposure may increase; NSAIDs can reduce diuresis and increase renal risk.
Urine alkalinization can reduce methenamine efficacy and prolong quinidine elimination; neuromuscular-blocking effects may be enhanced.

Adverse effects

Electrolyte depletion, especially hypokalemia

Preparations

Preparation	Form	Strength	Route
Chlorothiazide 250 mg tablet	Tablet	250 mg / tablet	PO
Chlorothiazide 500 mg tablet	Tablet	500 mg / tablet	PO
Chlorothiazide 50 mg/mL oral liquid	Oral Liquid	50 mg / mL	PO
Chlorothiazide 500 mg vial Strength is per vial; no final mL concentration is implied.	Injection	500 mg / vial	IV

Monitoring and Administration

Monitor electrolytes and calcium during prolonged therapy.

The livestock injection described in the formulation section is hydrochlorothiazide, not chlorothiazide. Do not use it as a chlorothiazide preparation or copy its injectable dose into this drug calculator.

Reconstituted chlorothiazide injection is described as stable for 24 hours.

Monitor hydration, electrolytes, glucose, BUN, creatinine and blood pressure as appropriate. Protect oral suspension from freezing.