Formulary
Losartan: Uses, Dosing, Side Effects and Indian Brand Names
Losartan is the first angiotensin receptor blocker, notable for its landmark LIFE trial evidence, unique uricosuric property, and role as an alternative to ACE inhibitors in patients with cough.
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Losartan: Uses, Dosing, Side Effects and Indian Brand Names
Losartan is the first angiotensin receptor blocker, notable for its landmark LIFE trial evidence, unique uricosuric property, and role as an alternative to ACE inhibitors in patients with cough.
NEET PG High-Yield: LIFE trial (losartan superior to atenolol in hypertension with LVH). Uricosuric property unique among ARBs -- favourite MCQ point. Prodrug metabolised by CYP2C9/CYP3A4. No bradykinin accumulation = no cough. RENAAL trial for diabetic nephropathy. Telmisartan has the longest half-life among ARBs and PPAR-gamma activity -- compare/contrast is frequently tested.
Clinical overview
Losartan was the first angiotensin II receptor blocker (ARB) to be marketed and remains one of the most prescribed in India. The landmark LIFE trial (Losartan Intervention For Endpoint reduction) demonstrated that losartan was superior to atenolol in reducing cardiovascular morbidity and mortality in hypertensive patients with left ventricular hypertrophy, with a particularly striking reduction in stroke risk. This trial was pivotal in downgrading beta-blockers from first-line hypertension therapy. Losartan has a unique pharmacological property among ARBs: it is uricosuric, reducing serum uric acid levels by inhibiting the URAT1 transporter in the proximal tubule. This makes it the preferred ARB in patients with coexisting hyperuricaemia or gout -- a commonly tested point in NEET PG. Losartan is a prodrug, converted by hepatic cytochrome P450 enzymes (primarily CYP2C9 and CYP3A4) to its active metabolite EXP-3174, which is 10-40 times more potent and has a longer half-life. The RENAAL trial demonstrated renoprotective benefits in type 2 diabetic nephropathy. ARBs are the alternative for patients who develop ACE inhibitor cough, sharing the same contraindications regarding pregnancy, bilateral renal artery stenosis, and hyperkalaemia. In Indian practice, losartan and telmisartan are the two most popular ARBs, with telmisartan favoured for its longer half-life and PPAR-gamma agonist activity.
Pharmacological class
Losartan belongs to the Angiotensin II Receptor Blockers (ARBs/Sartans) class. Selectively blocks the angiotensin II type 1 (AT1) receptor, preventing angiotensin II-mediated vasoconstriction, aldosterone secretion, and sympathetic activation. Unlike ACE inhibitors, it does not inhibit kininase II, so bradykinin is metabolised normally -- explaining the absence of dry cough. Also has a unique uricosuric effect not shared by other ARBs.
Indian brand names and formulations
Available as: Losar (Unichem), Losacar (Cadila), Repace (Sun Pharma), Covance (Ranbaxy/Sun).
Tablets: 25 mg, 50 mg, 100 mg. Fixed-dose combinations available with hydrochlorothiazide (Losar-H, Repace-H) and with amlodipine.
Regulatory status
Losartan is classified under Schedule H in India under the Drugs and Cosmetics Act, 1940. Prescription-only. Listed on NLEM. Widely available across India.
Indications
- Hypertension (first-line, especially when ACE inhibitor cough occurs)
- Diabetic nephropathy in type 2 diabetes (RENAAL trial)
- Heart failure when ACE inhibitors are not tolerated
- Hypertension with left ventricular hypertrophy (LIFE trial)
- Hyperuricaemia with hypertension (unique uricosuric effect)
Dosing
Adults: 50 mg once daily, may increase to 100 mg once daily. Hepatic impairment: start at 25 mg. No routine dose adjustment in renal impairment, but not recommended when GFR <30 mL/min without close monitoring. Volume-depleted patients: start at 25 mg.
Contraindications
- Pregnancy (teratogenic -- same mechanism as ACE inhibitors)
- Bilateral renal artery stenosis
- Hyperkalaemia (K+ >5.5 mEq/L)
- Severe hepatic impairment (reduced prodrug activation)
- Concomitant aliskiren use in diabetic patients
Adverse effects
- Dizziness and orthostatic hypotension (especially in volume-depleted patients)
- Hyperkalaemia (less common than with ACE inhibitors, but same risk factors apply)
- Fatigue
- Upper respiratory tract infection (reported in trials, though causality debated)
- Angioedema (very rare, much less than ACE inhibitors, but cross-reactivity possible)
Drug interactions
- Potassium-sparing diuretics: risk of hyperkalaemia; same cautions as ACE inhibitors
- NSAIDs: reduce antihypertensive effect, increase AKI risk
- Rifampicin: induces CYP enzymes, may reduce active metabolite levels and efficacy
- Lithium: reduced renal clearance, risk of lithium toxicity
- Fluconazole: inhibits CYP2C9, may reduce conversion to active metabolite (but may also increase parent drug levels)
Pregnancy and lactation
Contraindicated throughout pregnancy. Category D (2nd/3rd trimester). Causes foetal renal failure, oligohydramnios, and skeletal abnormalities. Discontinue immediately if pregnancy is detected.
Exam-style clinical scenario
A 58-year-old man with hypertension, gout, and LVH on echocardiography is currently on atenolol. His uric acid is elevated at 8.5 mg/dL. Which antihypertensive switch addresses all three concerns? Losartan -- it has proven superiority over atenolol in hypertension with LVH (LIFE trial) and its unique uricosuric effect helps manage hyperuricaemia.
Cost in India
Rs 30-80 for a strip of 10 tablets (50 mg). Available at Jan Aushadhi centres.
Clinical governance
Author: MedNext Editorial Team. Clinical reviewer: Awaiting clinical review. Jurisdiction: India (Drugs and Cosmetics Act, 1940). Sources: CIMS India, Indian Pharmacopoeia. Publication state: Awaiting clinical review. Correction: Report errors at support@mednext.academy.
Frequently Asked Questions
Why is losartan preferred over other ARBs in gout?
Losartan is the only ARB with a clinically significant uricosuric effect. It inhibits the URAT1 transporter in the proximal renal tubule, reducing uric acid reabsorption and increasing urinary uric acid excretion. This can lower serum uric acid by 0.5-1.0 mg/dL. Other ARBs (telmisartan, valsartan, irbesartan) lack this property.
Can a patient who had angioedema with an ACE inhibitor take losartan?
Use with extreme caution. Cross-reactivity for angioedema between ACE inhibitors and ARBs is approximately 2-8%. While ARBs are the usual alternative for ACE inhibitor cough, angioedema is a more serious concern. Some guidelines suggest a 6-week washout before starting an ARB, with close monitoring. In some high-risk cases, a CCB or thiazide may be safer.
How does losartan compare with telmisartan for NEET PG?
Losartan: prodrug, uricosuric, CYP2C9 metabolism, shorter half-life (6-9 h for active metabolite), LIFE and RENAAL trials. Telmisartan: not a prodrug, longest half-life of all ARBs (24 h), PPAR-gamma partial agonist (mild insulin-sensitising effect), no uricosuric effect, ONTARGET trial.
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