Hydrochlorothiazide

Hydrochlorothiazide: Uses, Dosage and Side Effects

Overview

• Thiazide diuretic inhibits the reabsorption of sodium and chloride in the distal convoluted tubule by blocking the sodium/ chloride symporter, resulting in sodium, chloride and water loss in the urine.
• It also causes excretion of potassium, magnesium and bicarbonate.
• It is formulated with a potassium-sparing diuretic (amiloride).

Uses of Hydrochlorothiazide

• Additional therapy for congestive heart failure when the clinical signs have become refractory to furosemide/torasemide.
• However, loop-diuretic therapy should continue when using hydrochlorothiazide to gain the beneficial effect of sequential nephron blockade.
• Used in the prevention of calcium oxalate urolithiasis.
• Antihypertensive effects.

Dose of Hydrochlorothiazide in Dogs and Cats

Dogs:

• 0.5–4 mg/kg p.o. q12–24h.
• Start at a low dose and titrate upwards every 5–10 days, to effect.
• Monitor urea, creatinine, electrolytes and blood pressure before increasing dose.

Cats:

• 1–2 mg/kg p.o. q12–24h.
• Start at a low dose and titrate upwards cautiously as above.

Side Effects of Hydrochlorothiazide in Dogs and Cats

• Hyperglycaemia, hypokalemia, hyponatraemia, hypochloraemia and volume contraction.
• It enhances the effects of the renin-angiotensin-aldosterone system in heart failure.

Contraindications of Hydrochlorothiazide in Dogs and Cats

• Renal impairment, as it tends to reduce the glomerular filtration rate.

Some Notes:

• Increased possibility of hypokalemia developing if thiazides are used concomitantly with corticosteroids or loop diuretics (furosemide).
• Thiazide-induced hypokalaemia may increase the risk of digoxin toxicity.
• Concomitant use of potassium-sparing diuretics (e.g. spironolactone) or potassium
  supplementation may be necessary during prolonged administration.
• The concurrent administration of vitamin D or calcium salts with thiazides may exacerbate hypercalcaemia.