Adult: Initially, 12.5 or 25 mg daily given alone or w/ other antihypertensive; may increase to 50 mg daily if necessary. Elderly: Initially, 6.25-12.5 mg once daily or on alternate days. Max: 25 mg daily. Child: Initially, 0.5-1 mg/kg 48 hrly. Max: 1.7 mg/kg 48 hrly.
Adult: Initially, 25-50 mg daily given alone or w/ digitalis, ACE inhibitor, or both; may increase to 100-200 mg daily in severe cases. Maintenance: 25-50 mg daily or on alternate days. Child: Initially, 0.5-1 mg/kg 48 hrly. Max: 1.7 mg/kg 48 hrly.
Renal Impairment
CrCl (mL/min)
Dosage
<30
Contraindicated.
Hepatic Impairment
Severe: Contraindicated.
Administration
Should be taken with food.
Contraindications
Hypersensitivity to chlortalidone and other sulfonamide derivatives. Anuria, symptomatic hyperuricaemia (i.e. history of gout or uric acid calculi); refractory hypokalaemia, hyponatraemia, and hypercalcaemia; adrenal insufficiency (e.g. Addison’s disease), HTN during pregnancy. Severe hepatic or renal (CrCl <30 mL/min) impairment. Concomitant lithium therapy.
Special Precautions
Patient w/ DM, moderate-high cholesterol level, SLE, history of allergy or bronchial asthma. Patient undergoing surgery. Childn, elderly. Hepatic (e.g. cirrhosis) or renal (e.g. nephrotic syndrome) impairment. Pregnancy and lactation.
This drug can cause dizziness, if affected, do not drive or operate machinery. Avoid long-term sun exposure.
Monitoring Parameters
Monitor BP, serum electrolytes, renal function, wt, and intake/output records (daily to determine fluid loss).
Overdosage
Symptoms: Dizziness, nausea, somnolence, hypovolaemia, hypotension, electrolyte disturbance, cardiac arrhythmia, muscle spasm. Management: Employ gastric lavage or activated charcoal, or induce emesis. Monitor BP, fluid, and electrolytes w/ appropriate corrective measures taken. Admin of IV fluid, electrolyte replacement, and artificial plasma supplementation may be beneficial.
Drug Interactions
Increased hypokalaemic effect w/ corticosteroids, amphotericin, carbenoxolone, ACTH, and β2-agonists. Reduced diuretic and antihypertensive effects w/ NSAIDs (e.g. indometacin). May increase the effects of antihypertensive agents and curare derivatives. May reduce therapeutic effects of insulin, oral antidiabetic agents, and oral anticoagulants. May induce cardiac arrhythmia w/ digitalis. May increase risk of hyperuricaemia and gout-type complications w/ ciclosporin. Potentially Fatal: May cause rapid increase in serum lithium levels, leading to toxicity.
Lab Interference
May increase the para amino benzoic acid (PABA) percentage during bentiromide test.
Action
Description: Mechanism of Action: Chlortalidone, a phthalimidine derivative of benzenesulfonamide, has actions similar to thiazide diuretics even though it does not contain a thiazide ring system. It inhibits Na and Cl reabsorption in the cortical-diluting segment of the ascending loop of Henle, thereby leading to increased secretion and excretion of K and hydrogen ions. Additionally, it promotes Ca reabsorption. Onset: Approx 2.6 hr. Duration: 48-72 hr. Pharmacokinetics: Absorption: Erratically absorbed from the GI tract. Bioavailability: Approx 64%. Time to peak plasma concentration: 8-12 hr. Distribution: Extensively distributed in erythrocytes. Crosses the placenta and enters breast milk. Plasma protein binding: Approx 75%, 58% to albumin. Metabolism: Metabolised in the liver. Excretion: Via urine (approx 70%, mainly as unchanged drug). Elimination half-life: 40-60 hr.
Chemical Structure
Chlortalidone Source: National Center for Biotechnology Information. PubChem Database. Chlorthalidone, CID=2732, https://pubchem.ncbi.nlm.nih.gov/compound/Chlorthalidone (accessed on Jan. 21, 2020)
Storage
Store between 20-25°C. Protect from light and moisture.
C03BA04 - chlortalidone ; Belongs to the class of low-ceiling sulfonamide diuretics.
References
AFT Pharmaceuticals Ltd. Hygroton 25 mg Tablets data sheet 19 September 2016. Medsafe. http://www.medsafe.govt.nz/. Accessed 22/02/2017.Anon. Chlorthalidone. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 22/02/2017.Buckingham R (ed). Chlortalidone. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 22/02/2017.Joint Formulary Committee. Chlortalidone. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 22/02/2017.McEvoy GK, Snow EK, Miller J et al (eds). Chlorthalidone. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 22/02/2017.Preston CL (ed). Lithium + Diuretics; Thiazide and Related. Stockley’s Drug Interactions [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 24/03/2017.
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