Adult: 25-100 mg daily in 1-2 divided dose. Max: 200 mg daily. Dose may be administered on alternate days or on 3-5 days each week. Child: <6 months 3 mg/kg daily in 2 divided doses; 6 months to<2 years 1-2 mg/kg daily as single or in 2 divided doses. Max: 37.5 mg daily; 2-12 years 1-2 mg/kg daily as single or in 2 divided doses. Max: 100 mg daily. Elderly: >65 years Initially, 12.5 mg daily, titrate as necessary in increments of 12.5 mg.
Oral Hypertension
Adult: As monotherapy or in combination with other antihypertensives: Initially, 12.5 mg daily, may be increased up to 50 mg daily as necessary. Max: 100 mg daily. Dosage is individualised according to patient response. Child: <6 months 3 mg/kg daily in 2 divided doses; 6 months to <2 years 1-2 mg/kg daily as single or in 2 divided doses. Max: 37.5 mg daily; 2-12 years 1-2 mg/kg daily as single or in 2 divided doses. Max: 100 mg daily. Elderly: >65 years Initially, 12.5 mg daily, titrate as necessary in increments of 12.5 mg.
Administration
Should be taken with food.
Contraindications
Hypersensitivity to sulfonamide-derived drugs. Anuria.
Special Precautions
Patient with fluid or electrolyte imbalance, Addison’s disease, ascites due to cirrhosis, prediabetes or diabetes mellitus, hypercholesterolaemia, bronchial asthma, SLE, gout. Postoperative period after bariatric surgery. Hepatic and severe renal impairment. Children and elderly. Pregnancy and lactation.
This medicine may cause photosensitivity reactions, avoid exposure to direct sunlight and UV light and apply sunscreen when going outdoors.
Monitoring Parameters
Monitor serum electrolytes (e.g. Na, K), blood pressure, BUN, creatinine. Assess skin for photosensitivity and skin cancer; visual acuity and ocular pain.
Overdosage
Symptoms: Electrolyte depletion (e.g. hypokalaemia, hypochloraemia, hyponatraemia), and dehydration. Management: Symptomatic and supportive treatment. May induce emesis or perform gastric lavage for recent ingestion. Administration of activated charcoal may be given within 1 hour of ingestion. Correct dehydration, electrolyte imbalance, hepatic coma, and hypotension by established procedures. Give oxygen or artificial respiration for respiratory impairment as needed.
Drug Interactions
May reduce renal clearance and enhance the toxic effect of lithium. Potentiation of orthostatic hypotension with alcohol, barbiturates, or narcotics. May reduce therapeutic effect of antidiabetics. Additive effect with other antihypertensive drugs. Reduced absorption with cholestyramine and colestipol resins. Enhanced hypokalaemic effect with corticosteroids, ACTH. May decrease arterial response to pressor amines (e.g. norepinephrine). May increase response to neuromuscular blocking action of skeletal muscle relaxants (e.g. tubocurarine).
Food Interaction
May potentiate orthostatic hypotension with alcohol.
Lab Interference
May interfere with parathyroid function tests. May cause false positive result to aldosterone/renin ratio (ARR).
Action
Description: Hydrochlorothiazide is a thiazide diuretic which acts by inhibiting Na reabsorption in the distal tubules, thereby causing increased excretion of Na, K, hydrogen ions, and water. The hypotensive effects are initially due to volume reduction, but the persisting effect includes other undetermined mechanisms that reduce peripheral resistance. Onset: Diuresis: Approx 2 hours. Peak effect: Approx 4 hours. Duration: 6-12 hours. Pharmacokinetics: Absorption: Rapidly and fairly well absorbed from the gastrointestinal tract. Bioavailability: Approx 65-75%. Time to peak plasma concentration: Approx 1-5 hours. Distribution: Crosses placenta, enters breast milk. Volume of distribution: 3.6-7.8 L/kg. Plasma protein binding: Approx 40-68%. Excretion: Mainly via urine (≥61% as unchanged drug). Elimination half-life: Approx 5-15 hours.
Chemical Structure
Hydrochlorothiazide Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 3639, Hydrochlorothiazide. https://pubchem.ncbi.nlm.nih.gov/compound/Hydrochlorothiazide. Accessed Feb. 23, 2023.
Storage
Store between 20-25°C. Protect from light and moisture.
C03AA03 - hydrochlorothiazide ; Belongs to the class of low-ceiling thiazide diuretics.
References
Anon. Hydrochlorothiazide. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 01/09/2022.Anon. Hydrochlorothiazide. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 01/09/2022.Apo-Hydrochlorothiazide 25 mg and 50 mg Tablets (Apotex Inc.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 01/09/2022.Buckingham R (ed). Hydrochlorothiazide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 01/09/2022.Hydrochlorothiazide Capsules (Aurobindo Pharma Limited). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 01/09/2022.Hydrochlorothiazide Tablets (Teva Pharmaceuticals). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 01/09/2022.Joint Formulary Committee. Hydrochlorothiazide. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 01/09/2022.
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