1. Clinical & Scientific Overview
Losartan Potassium (TIP-MED-000003, Reference Code [3.3]) is classified under
Cardiovascular & Antithrombotic Medicines (Ch 03) as a Angiotensin II Receptor Blocker (ARB; selective AT1 antagonist).
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).
Losar (Unichem), Losacar (Zydus), Repace (Sun Pharma), Tozaar (Torrent)
Oral Film-Coated Tablets: 25 mg, 50 mg, 100 mg
3. Mechanism of Action & Pharmacodynamics
Blocks AT1 receptor-mediated vasoconstriction and aldosterone secretion; converted via hepatic CYP2C9/CYP3A4 to active carboxylic acid metabolite E-3174 (10–40x more potent) + unique URAT1-mediated uricosuric effect
4. Therapeutic Indications & Evidence-Supported Uses
- Hypertension (especially with concurrent hyperuricaemia/gout or left ventricular hypertrophy)
- diabetic nephropathy with proteinuria in Type 2 DM
- heart failure (when ACE inhibitors are not tolerated)
5. Educational Dosage Context, Formulations & Administration
Educational Dosing & Regimen Summary: General Adult Reference: Initially 50 mg once daily (25 mg OD in intravascular volume depletion or hepatic impairment); may increase to 100 mg once daily or 50 mg twice daily. Follow physician prescription.
Administration & Meal Timing: With or without food (typically after breakfast). | Once daily in the morning, or divided twice daily (morning and evening) if 50 mg BD is prescribed for smoother 24-hour BP control.
6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment
Absorption, distribution, metabolism, and excretion follow class pharmacokinetic profile; verify patient renal/hepatic function.
Renal: No initial dose reduction required unless volume-depleted, but requires close monitoring of creatinine and K+ as eGFR declines; suspend during acute dehydrating illness ('Sick Day Rule'). Hepatic: Plasma concentrations doubled in cirrhosis—initiate at 25 mg once daily.
Renal: No initial dose reduction required unless volume-depleted, but requires close monitoring of creatinine and K+ as eGFR declines; suspend during acute dehydrating illness ('Sick Day Rule'). Hepatic: Plasma concentrations doubled in cirrhosis—initiate at 25 mg once daily.
Renal: No initial dose reduction required unless volume-depleted, but requires close monitoring of creatinine and K+ as eGFR declines; suspend during acute dehydrating illness ('Sick Day Rule'). Hepatic: Plasma concentrations doubled in cirrhosis—initiate at 25 mg once daily.
7. Contraindications, Precautions & High-Risk Warnings
- Contraindicated in pregnancy, lactation, and bilateral renal artery stenosis. Requires CYP2C9 conversion to its active E-3174 metabolite for full potency.
Key Clinical Precautions: Renal: No initial dose reduction required unless volume-depleted, but requires close monitoring of creatinine and K+ as eGFR declines; suspend during acute dehydrating illness ('Sick Day Rule'). Hepatic: Plasma concentrations doubled in cirrhosis—initiate at 25 mg once daily.
8. Adverse Effects Profile
- Dizziness, nasal congestion, fatigue, mild hyperkalaemia, transient musculoskeletal ache.
- Severe hyperkalaemia, acute renal failure in renal artery stenosis, rare angioedema, hepatotoxicity.
- Monitor for severe hypersensitivity, organ toxicity, or dose-limiting adverse events.
9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions
- Potassium-sparing diuretics (Spironolactone, Eplerenone), K+ supplements, or salt substitutes (LoSalt) -> severe hyperkalaemia
- NSAIDs -> blunted antihypertensive effect and acute kidney injury ('Triple Whammy' with diuretic)
- Lithium -> reversible lithium toxicity
- CYP2C9 inducers (Rifampicin) reduce active E-3174 metabolite and lower BP efficacy; Fluconazole inhibits conversion to E-3174 (clinical significance: monitor BP response over 1–2 weeks)
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: Highlight that losartan uniquely lowers serum uric acid mildly by inhibiting renal URAT1 reabsorption, making it particularly advantageous in hypertensive patients prone to gout. Maintain adequate hydration during initial weeks.
- Meal & Clock Timing Instruction: With or without food (typically after breakfast). (Once daily in the morning, or divided twice daily (morning and evening) if 50 mg BD is prescribed for smoother 24-hour BP control.)
- Missed Dose Protocol: Take as soon as remembered unless within 6–8 hours of the next scheduled dose. Do not double the dose.
- Geriatric Dispensing Pearl: Shorter half-life than telmisartan (parent drug ~2 h, active metabolite ~6–9 h); some elderly patients experience evening BP breakthrough on once-daily dosing and may be prescribed 25–50 mg BD. Initiate at 25 mg in patients >75 years or on diuretics.
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 Film-Coated Tablets: 25 mg, 50 mg, 100 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 [3.3] (p. 22)
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.