amiloride hydrochloride + hydrochlorothiazide: clinical use

Prescribing considerations

• Review all potassium-raising treatments.
• Use particular caution in older people and in cardiac, hepatic or renal disease because electrolyte disturbances and high potassium may develop rapidly.
• Hydrochlorothiazide has a cumulative exposure-related association with non-melanoma skin cancer; advise sun protection, skin surveillance and review previous skin cancer.
• Consider effects on glucose tolerance, urate, calcium, lipids and parathyroid-function testing.

Contraindications and cautions

• High potassium or concurrent potassium-conserving diuretics; potassium supplementation without a carefully monitored exception
• Severe renal impairment, progressive renal disease, acute renal failure or anuria
• Severe hepatic failure or cirrhotic precoma
• Concurrent lithium therapy
• Addison's disease or hypercalcaemia
• Hypersensitivity to either active substance, sulfonamide-derived drugs or an excipient; wheat allergy

Monitoring

• Blood pressure, volume status and clinical response
• Serum potassium, sodium, magnesium and other electrolytes
• Renal function and blood urea
• Glucose where clinically relevant and urate in people with gout risk
• Skin for new or changing lesions

Clinical pharmacology

Hydrochlorothiazide inhibits tubular sodium and chloride reabsorption, producing sodium loss, diuresis and potassium loss. Amiloride reduces distal sodium reabsorption and limits potassium secretion. Both components are substantially eliminated unchanged, making renal function clinically important.

Formulation and product differences

• The selected product is an oral, scored tablet; the score is for easier swallowing and not equal subdivision.
• It contains lactose and wheat starch. Its very low gluten content is unlikely to affect coeliac disease, but it must not be used in wheat allergy.
• The tablets should be protected from light.