1. Clinical & Scientific Overview
Hydrochlorothiazide (HCTZ) (TIP-MED-000012, Reference Code [3.12]) is classified under
Cardiovascular & Antithrombotic Medicines (Ch 03) as a Thiazide Diuretic (Distal Convoluted Tubule Na+/Cl- Cotransporter Inhibitor).
Within the Indian regulatory and compendial framework, it is governed under Schedule H Prescription Drug (To be sold by retail on the prescription of a Registered Medical Practitioner only — Drugs Rules 1945).
Carloc (Cipla), Cardivas (Sun Pharma), Carca (Intas)
Oral Uncoated Tablets: 12.5 mg, 25 mg
3. Mechanism of Action & Pharmacodynamics
Thiazide Diuretic (Distal Convoluted Tubule Na+/Cl- Cotransporter Inhibitor) acting on target receptor/enzyme pathways in Cardiovascular & Antithrombotic Medicines (Ch 03): clinical efficacy is mediated via Thiazide Diuretic (Distal Convoluted Tubule Na+/Cl- Cotransporter Inhibitor) for Hypertension (alone or in FDC with ARB/ACEI/beta-blocker); mild-to-moderate oedema; idiopathic hypercalciuria / calcium nephrolithiasis prevention..
4. Therapeutic Indications & Evidence-Supported Uses
- Hypertension (alone or in FDC with ARB/ACEI/beta-blocker)
- mild-to-moderate oedema
- idiopathic hypercalciuria / calcium nephrolithiasis prevention
🇮🇳 Jurisdiction & Indication Note: Indications and schedules reflect Indian compendial and regulatory records (CDSCO / Indian Pharmacopoeia & NFI / NLEM 2022). Where international reference labels (US FDA DailyMed / NCBI StatPearls) are cited for pharmacokinetic or mechanistic parameters, international approvals do not automatically imply CDSCO approval in India.
5. Educational Dosage Context, Formulations & Administration
Educational Dosing & Regimen Summary: General Adult Reference: Hypertension: 12.5 mg to 25 mg once daily in the morning (doses >25 mg/day rarely needed). Oedema: 25–50 mg daily. Follow physician prescription.
Administration & Meal Timing: With or after breakfast. | Standard OPD schedule: Once daily in the morning (08:00–09:00 AM) to prevent nocturia and sleep disruption (or as directed by prescriber).
6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment
Absorption, distribution, metabolism, and excretion follow class pharmacokinetic profile; verify patient renal/hepatic function.
Renal: loses natriuretic efficacy when eGFR <30 mL/min (switch to a loop diuretic like torsemide or furosemide if volume overload is present). Hepatic: May precipitate hepatic coma in decompensated cirrhosis via hypokalaemia.
Renal: loses natriuretic efficacy when eGFR <30 mL/min (switch to a loop diuretic like torsemide or furosemide if volume overload is present). Hepatic: May precipitate hepatic coma in decompensated cirrhosis via hypokalaemia.
Renal: loses natriuretic efficacy when eGFR <30 mL/min (switch to a loop diuretic like torsemide or furosemide if volume overload is present). Hepatic: May precipitate hepatic coma in decompensated cirrhosis via hypokalaemia.
7. Contraindications, Precautions & High-Risk Warnings
- Contraindicated in anuria, severe renal failure (CrCl <30 mL/min—ineffective as diuretic), acute gout, refractory hypokalaemia/hyponatraemia, and sulfonamide allergy. Caution in diabetes mellitus and dyslipidaemia.
Key Clinical Precautions: Renal: loses natriuretic efficacy when eGFR <30 mL/min (switch to a loop diuretic like torsemide or furosemide if volume overload is present). Hepatic: May precipitate hepatic coma in decompensated cirrhosis via hypokalaemia.
8. Adverse Effects Profile
- Increased urinary frequency, hypokalaemia, hyponatraemia, hypomagnesaemia, hyperuricaemia, mild increase in fasting blood glucose and LDL/triglycerides, erectile dysfunction, photosensitivity.
- Symptomatic hyponatraemia, severe hypokalaemia with ventricular ectopy, acute angle-closure glaucoma (idiosyncratic choroidal effusion—presents with acute eye pain/blurred vision within hours to weeks), acute gout attack.
- Monitor for severe hypersensitivity, organ toxicity, or dose-limiting adverse events.
9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions
- Digoxin and QT-prolonging agents (increased arrhythmia risk if hypokalaemic)
- Lithium (markedly reduced renal lithium excretion)
- NSAIDs (blunted antihypertensive response and AKI)
- Corticosteroids and beta-2 agonists (additive hypokalaemia)
- Cholestyramine reduces HCTZ absorption
10. Clinical Monitoring, Patient Counselling & Storage
Clinical & Laboratory Monitoring: Monitor clinical response, baseline renal/hepatic parameters, and relevant serum biomarkers.
Pharmacist Patient Counselling Points:
- Patient Counselling Checklist: Take in the morning after breakfast. Use sun protection (umbrella/sunscreen) during peak Indian summer sunlight, as HCTZ sensitises the skin to UV rays. Pause during bouts of severe vomiting or diarrhoea ('Sick Day Rule').
- Meal & Clock Timing Instruction: With or after breakfast. (Standard OPD schedule: Once daily in the morning (08:00–09:00 AM) to prevent nocturia and sleep disruption (or as directed by prescriber).)
- Missed Dose Protocol: Take if remembered before mid-afternoon (02:00 PM); skip if remembered in the evening to avoid nocturia.
- Geriatric Dispensing Pearl: Included in Beers Criteria as requiring caution due to SIADH-like hyponatraemia risk. When paired with an ARB or ACE inhibitor (e.g., Telma-H), potassium loss is largely offset, but sodium loss (hyponatraemia) and dehydration risk remain significant in frail elderly patients.
Storage, Stability & Dispensing Safeguards: Store below 25°C–30°C in original moisture- and light-resistant packaging out of reach of children. Available forms: Oral Uncoated Tablets: 12.5 mg, 25 mg
11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)
12. Authoritative References, Regulatory Sources & Editorial Disclaimer
Primary Compendial & Guideline Reference: Indian Pharmacist Desk Reference — Professional Edition 2.7 (2026–27) • Ch 03 [3.12] (p. 26)
Official Verification Portals: Indian Pharmacopoeia Commission (IPC) & National Formulary of India (NFI) • Central Drugs Standard Control Organization (CDSCO) • Ministry of Health & Family Welfare — NLEM 2022 • NCBI Bookshelf / StatPearls Pharmacology Reference • DailyMed (US FDA Official Prescribing Reference)
Last Medically & Pharmaceutically Reviewed: 2026-11-10 • Verification Status: HANDBOOK_SOURCE_CONTENT
Educational & Clinical Disclaimer: This reference profile is published solely for pharmacy education, academic study, and professional clinical reference. It does not substitute for patient-specific clinical judgement, qualified specialist oncology/medical supervision, or official CDSCO/IP prescribing information. Never self-medicate with prescription, Schedule H/H1/X, NDPS, or oncology medicines.
13. Related Reference Monographs, Educational Guides & Visual Concept
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