Chlorthalidone

Indications

Chlorthalidone is used for: Hypertension, Oedema, Diabetes insipidus, Congestive heart failure

Adult Dose

Hypertension 25-100 mg/day PO; usual range, 12.5-25 mg/day Edema 50-100 mg/day PO or 100 mg PO every other day; not to exceed 200 mg/day Heart Failure 12.5-25 mg/day PO; not to exceed 100 mg/day

Child Dose

Renal Dose

Renal impairment CrCl <10 mL/min: Ineffective; do not use CrCl >10 mL/min: Dose adjustment not necessary

Administration

Should be taken with food. Take during meals.

Contra Indications

Severe renal impairment or anuria. Severe hepatic impairment, addison's disease, preexisting hypercalcaemia, asthma; hypersensitivity; severe allergy. Pregnancy and lactation.

Precautions

Existing fluid and electrolyte disturbances, hepatic cirrhosis, severe heart failure, hyperuricaemia, mild to moderate renal impairment. Elderly. Monitor fluid and electrolyte balance. Kidney or liver disease; diabetes; gout; hyperlipidaemia and ventricular extra systoles. Lactation: Drug enters breast milk; not recommended (American Academy of Pediatrics states that it is "compatible with nursing")

Pregnancy-Lactation

Pregnancy category: B; D (expert analysis); if used in gestational HTN.

Interactions

NSAIDs antagonise hypotensive action. Suppresses action of oral anticoagulants due to reduced prothrombin activity. Increased risk of hypokalaemia when corticosteroids are given concurrently. Potentially Fatal: Potentiates bone marrow suppression caused by anticancer drugs. Diuretic-induced vol depletion can potentiate aminoglycoside nephrotoxicity. Impairs action of oral hypoglycaemic agents. Enhances digitalis toxicity due to hypokalaemia. vol depletion enhances lithium toxicity, conversely, sudden withdrawal of diuretics may result in subtherapeutic levels of circulating lithium. Prolonged paralysis with tubocurarine due to hypokalaemia.

Adverse Effects

Side effects of Chlorthalidone : Common Cardiovascular: Hypotension, vasculitis Dermatologic: Photosensitivity, phototoxicity Endocrine/metabolic: Electrolyte abnormalities, hyperglycemia, hyperuricemia Gastrointestinal: Constipation, diarrhea, loss of appetite, nausea, vomiting Musculoskeletal: Spasticity Neurologic: Dizziness, headache, paresthesia Ophthalmologic: Blurred vision, xanthopsia Psychiatric: Restlessness Reproductive: Impotence Potentially Fatal: Rare. Severe hyponatraemia and idiosyncratic hypersensitivity.

Mechanism of Action

Chlortalidone is an oral, long acting antihypertensive/diuretic. It is a monosulfamyl diuretic that acts by enhancing the excretion of sodium and chloride ions, and water by interfering with the transport of sodium ions across the renal tubular epithelium. Their primary site of action appears to be at the cortical diluting segment in the nephron of the loop of Henle.