Losartan
losartan potassium · Brand: Cozaar
Losartan Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Hypertension | Adults & children ≥6 years | Monotherapy or combination | FDA Approved |
| Stroke risk reduction in hypertension with left ventricular hypertrophy | Adults (evidence does not support benefit in Black patients) | Monotherapy or with HCTZ | FDA Approved |
| Diabetic nephropathy — elevated serum creatinine & proteinuria (UACR ≥300 mg/g) | Adults with type 2 diabetes and hypertension | Adjunctive to conventional antihypertensive therapy | FDA Approved |
Losartan is the first orally available angiotensin II receptor blocker and remains one of the most widely prescribed antihypertensives globally. It carries three distinct FDA-approved indications, making it unique among ARBs. The LIFE trial (Lancet 2002) established its stroke risk reduction benefit in hypertensive patients with LVH, demonstrating a 25% relative risk reduction in stroke (HR 0.75, p=0.001) and a 25% reduction in new-onset diabetes compared to atenolol at similar blood pressure control. The RENAAL trial (NEJM 2001) confirmed its renoprotective properties in type 2 diabetic nephropathy, with a 28% reduction in progression to end-stage renal disease. Unlike ACE inhibitors, losartan does not cause bradykinin accumulation, resulting in a significantly lower incidence of dry cough.
Heart failure with reduced ejection fraction (HFrEF): ARBs are recommended as alternatives to ACE inhibitors in patients who are intolerant (primarily due to cough or angioedema) per AHA/ACC/HFSA guidelines (2022). Losartan is used in this context, though valsartan and candesartan have larger specific heart failure trial databases. Evidence quality: High (class effect).
Marfan syndrome — aortic root dilation: Based on emerging evidence that losartan may slow aortic root enlargement through TGF-β pathway modulation. Results have been mixed across trials. Evidence quality: Moderate.
Hyperuricaemia / Gout prophylaxis: Losartan is the only ARB with a clinically meaningful uricosuric effect, reducing serum uric acid by approximately 20–25%. May be preferred in hypertensive patients with co-existing gout. Evidence quality: Moderate.
Dosing
Adult Dosing by Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Essential hypertension — uncomplicated | 50 mg once daily | 50–100 mg/day | 100 mg/day | Full antihypertensive effect within 3–6 weeks; can be given QD or divided BID Consider adding HCTZ 12.5 mg if BP response insufficient at 100 mg |
| Hypertension — volume-depleted or on diuretics | 25 mg once daily | 50–100 mg/day | 100 mg/day | Lower starting dose reduces first-dose hypotension risk Correct volume depletion before initiation when possible |
| Stroke risk reduction — hypertension with LVH | 50 mg once daily | 50–100 mg/day | 100 mg/day | Add HCTZ 12.5 mg and/or increase to 100 mg; then HCTZ to 25 mg based on BP response Based on LIFE protocol; benefit not demonstrated in Black patients |
| Diabetic nephropathy — type 2 DM with proteinuria | 50 mg once daily | 100 mg once daily | 100 mg/day | Increase to 100 mg based on BP response; monitor SCr and K+ every 2–4 weeks during titration 71% of RENAAL patients received 100 mg; 2-year delay in need for dialysis |
Paediatric Dosing (Hypertension, ≥6 years)
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Paediatric hypertension (≥6 years, ≥20 kg) | 0.7 mg/kg once daily (max 50 mg) | Adjusted per BP response | 1.4 mg/kg/day (max 100 mg/day) | Available as oral suspension (2.5 mg/mL) for children unable to swallow tablets Not recommended in children <6 years or with eGFR <30 mL/min/1.73 m² |
Hepatic Impairment
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Mild to moderate hepatic impairment | 25 mg once daily | Per clinical response | Titrate cautiously | Bioavailability approximately doubled and plasma clearance reduced ~50% in hepatic impairment Not studied in severe hepatic impairment |
Losartan can be taken with or without food; food slows absorption but has only minor effects on overall exposure (~10% decrease in AUC). No renal dose adjustment is required, even in patients on haemodialysis, because neither losartan nor its active metabolite EXP3174 is removed by dialysis due to very high protein binding (98.7–99.8%). However, volume-depleted dialysis patients should start at 25 mg. Losartan has a unique uricosuric property among ARBs — consider it preferentially in hypertensive patients with hyperuricaemia or gout.
Pharmacology
Mechanism of Action
Losartan is a selective, competitive antagonist of the angiotensin II type 1 (AT1) receptor. Unlike ACE inhibitors, it blocks the downstream receptor rather than the enzyme that produces angiotensin II, meaning it does not inhibit bradykinin degradation. This explains the substantially lower incidence of dry cough compared with ACE inhibitors. Approximately 14% of an oral dose is converted by hepatic cytochrome P450 enzymes (primarily CYP2C9) to the active carboxylic acid metabolite EXP3174, which is 10–40 times more potent than the parent compound and acts as a non-competitive, insurmountable AT1 antagonist. At the 100 mg dose, losartan inhibits the angiotensin II pressor response by approximately 85% at peak, with 25–40% inhibition persisting at 24 hours. Beyond blood pressure reduction, losartan promotes LVH regression, reduces proteinuria through efferent arteriolar dilation, and uniquely among ARBs exerts a uricosuric effect that lowers serum uric acid levels.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Well absorbed orally; systemic bioavailability ~33% (extensive first-pass); Tmax ~1 h (losartan), 3–4 h (EXP3174); food slows absorption, minor AUC effect (~10% decrease) | Low bioavailability is offset by potent active metabolite with 4-fold greater AUC; can be taken regardless of meals |
| Distribution | Vd 34 L (losartan), 12 L (EXP3174); protein binding 98.7% (losartan), 99.8% (EXP3174) to albumin; minimal CNS penetration | Very high protein binding means drug not removed by haemodialysis; displacement interactions unlikely at therapeutic concentrations |
| Metabolism | CYP2C9 (primary) and CYP3A4; ~14% converted to active metabolite EXP3174 (10–40x more potent); additional inactive metabolites formed | CYP2C9 poor metabolisers or co-administration of CYP2C9 inhibitors may increase losartan and decrease EXP3174 levels; consider pharmacogenomic testing in non-responders |
| Elimination | t½ ~2 h (losartan), 6–9 h (EXP3174); total plasma clearance 600 mL/min (losartan), 50 mL/min (EXP3174); ~35% excreted in urine, ~60% in faeces; 4% unchanged in urine | No renal dose adjustment required; neither compound removed by dialysis; biliary excretion is a major elimination pathway; hepatic impairment requires dose reduction |
Side Effects
Losartan was evaluated for safety in more than 3,300 adult patients with essential hypertension. The overall incidence of adverse events was similar to placebo. The RENAAL trial (1,513 patients with diabetic nephropathy) and the LIFE trial (9,193 patients with HTN and LVH) provided additional safety data.
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Hyperkalemia | ≥4% excess vs placebo (RENAAL) | Particularly common in diabetic nephropathy patients due to baseline renal impairment; monitor K+ closely; avoid concomitant K-sparing agents |
| Hypotension / Orthostatic hypotension | ≥4% excess vs placebo (RENAAL) | More frequent in the diabetic nephropathy population; volume status assessment essential before initiation |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Upper respiratory infection | 8% (vs 7% placebo) | Marginally above placebo; managed symptomatically |
| Dizziness | 3% (vs 2% placebo) | Dose-related; usually transient during initial titration; assess orthostatic component in elderly |
| Nasal congestion | 2% (vs 1% placebo) | Mild; rarely warrants dose modification |
| Back pain | 2% (vs 1% placebo) | Musculoskeletal; evaluate in context of overall symptom profile |
| Headache | 1–3% | Similar to placebo in controlled trials; self-limiting |
| Asthenia / Fatigue | 2–4% (RENAAL) | More common in the diabetic nephropathy population; assess for excessive BP lowering |
| Diarrhoea | 2–4% (RENAAL) | More frequent in RENAAL population with background comorbidities |
| Anaemia | ≥2% excess (RENAAL) | May relate to RAAS blockade reducing erythropoietin; monitor haemoglobin in CKD patients |
| Cough | ~3% (significantly lower than ACE inhibitors) | In head-to-head studies, losartan cough rate (17–29%) was similar to HCTZ/placebo and far below lisinopril (62–69%) in ACEi-cough-prone patients |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Angioedema | Rare (postmarketing) | Any time | Discontinue immediately; emergency airway management if tongue/larynx involved; do not rechallenge; cross-reactivity with ACE inhibitor angioedema possible |
| Acute renal failure | Uncommon | Days to weeks, especially with renal artery stenosis or volume depletion | Discontinue or reduce dose; volume resuscitate; evaluate for bilateral renal artery stenosis; monitor creatinine closely during initiation |
| Severe hyperkalemia (K+ >6.0 mEq/L) | Uncommon in HTN; more common in CKD/DKD | Weeks to months | Hold losartan; treat with standard hyperkalaemia protocol; reassess concomitant K-elevating medications; consider potassium binder if restarting |
| Hepatitis / Hepatic dysfunction | Rare (postmarketing) | Variable | Discontinue; monitor LFTs; consider alternative antihypertensive class |
| Rhabdomyolysis | Very rare (postmarketing) | Variable | Discontinue; check CK; aggressive IV hydration; monitor renal function |
| Thrombocytopenia | Rare (postmarketing) | Variable | Discontinue; monitor platelet count; haematology referral if severe or persistent |
| Reason for Discontinuation | Incidence | Context |
|---|---|---|
| Overall adverse events | 2.3% | HTN trials; lower than placebo (3.7%) |
| Dizziness | <1% | Usually first-dose related; rarely leads to permanent discontinuation |
| Hypotension | <1% | Volume-depletion related; manageable with dose reduction |
In controlled cough studies comparing losartan with lisinopril in patients with documented ACE inhibitor cough, the losartan cough rate (17–29%) was similar to HCTZ or placebo, while lisinopril rates were 62–69%. This makes losartan an appropriate alternative for patients who discontinue ACE inhibitors due to cough, while maintaining comparable RAAS blockade benefits.
Drug Interactions
Losartan is metabolised via CYP2C9 and CYP3A4, giving it a pharmacokinetic interaction profile distinct from most other ARBs. Its active metabolite EXP3174 is primarily responsible for the antihypertensive effect. Pharmacodynamic interactions relate to potassium homeostasis and renal haemodynamics, similar to ACE inhibitors.
Monitoring
- Blood PressureEach visit; 2–4 weeks after dose changes
RoutineFull antihypertensive effect may take 3–6 weeks. Monitor seated and standing BP at initiation. For LIFE-type patients with LVH, target BP per current guideline recommendations. - Serum PotassiumBaseline, 1–2 weeks after initiation, then periodically
RoutineLosartan reduces aldosterone-mediated K+ excretion. Higher risk with renal impairment, diabetes, concomitant K-sparing agents, or K+ supplements. Hold if K+ >5.5 mEq/L. - Renal FunctionBaseline, 1–2 weeks after initiation, then every 3–6 months
RoutineCheck serum creatinine and eGFR. A rise of up to 30% in creatinine is acceptable if stable. In diabetic nephropathy, monitor every 2–4 weeks during dose titration. Investigate if >30% rise or progressive decline. - Hepatic FunctionIf signs of hepatic injury develop
Trigger-basedRare postmarketing reports of hepatitis. Discontinue if jaundice or significant transaminase elevation occurs. Use reduced starting dose (25 mg) in known hepatic impairment. - Haemoglobin / HaematocritPeriodically in CKD patients
Trigger-basedAnaemia reported in RENAAL (RAAS blockade may reduce erythropoietin production). Monitor in patients with CKD stage 3–5 who may already have renal anaemia. - Uric AcidBaseline if gout history; periodically if relevant
Trigger-basedLosartan uniquely lowers serum uric acid among ARBs (approximately 20–25% reduction). This can be tracked as an additional benefit in patients with hyperuricaemia or gout.
Contraindications & Cautions
Absolute Contraindications
- Hypersensitivity: Known allergy to losartan or any component of the formulation.
- Pregnancy: Contraindicated at any stage; direct fetal toxicity including oligohydramnios, renal failure, skull hypoplasia, and death (FDA Boxed Warning).
- Aliskiren co-administration in diabetes: Contraindicated due to increased risk of renal impairment, hypotension, and hyperkalemia.
Relative Contraindications (Specialist Input Recommended)
- Bilateral renal artery stenosis or stenosis of a solitary kidney: High risk of acute renal failure from loss of angiotensin II-mediated efferent arteriolar tone.
- Severe hepatic impairment: Losartan has not been studied in severe hepatic disease. Bioavailability is approximately doubled and clearance halved even in mild-to-moderate impairment; use with extreme caution under hepatology guidance.
- Severe volume depletion: Risk of symptomatic hypotension; correct volume status before initiation or start at 25 mg with close monitoring.
Use with Caution
- Renal impairment: No dose adjustment needed, but monitor potassium and creatinine closely. Not recommended in paediatric patients with GFR <30 mL/min/1.73 m².
- Heart failure: Risk of hypotension and renal deterioration; initiate at low dose with close haemodynamic monitoring.
- Black patients with hypertension and LVH: The LIFE trial did not demonstrate stroke risk reduction benefit in this subgroup. Consider alternative strategies for stroke prevention.
- CYP2C9 poor metabolisers: May have higher losartan levels and lower active metabolite levels. Clinical significance varies; monitor BP response.
When pregnancy is detected, discontinue losartan as soon as possible. Drugs acting directly on the renin-angiotensin system can cause injury and death to the developing fetus, including oligohydramnios, fetal renal failure, hypotension, skull hypoplasia, and neonatal death. Women of childbearing potential should be counselled about the risks and use reliable contraception during treatment.
Patient Counselling
Purpose of Therapy
Losartan works by blocking a hormone called angiotensin II that causes blood vessels to tighten. By blocking this hormone at its receptor, losartan helps blood vessels relax, lowering blood pressure and reducing strain on the heart and kidneys. Depending on why it was prescribed, it may protect against stroke, slow kidney disease progression, or simply control blood pressure.
How to Take
Take losartan once daily, at the same time each day, with or without food. Do not stop taking it without consulting your doctor, even if you feel well. If you miss a dose, take it as soon as you remember unless it is nearly time for your next dose. Keep well hydrated, especially during illness, hot weather, or exercise, as dehydration can cause blood pressure to drop too low.
Sources
- Cozaar (losartan potassium) tablets prescribing information. Merck Sharp & Dohme Corp. Revised October 2018. FDA Label PDFCurrent FDA-approved prescribing information; primary source for all dosing, contraindications, adverse reactions, drug interactions, and pharmacokinetic data.
- Losartan potassium tablets prescribing information. DailyMed / NLM. DailyMed LabelGeneric losartan labeling with updated formulation details and generic availability information.
- Dahlof B, Devereux RB, Kjeldsen SE, et al. Cardiovascular morbidity and mortality in the Losartan Intervention For Endpoint reduction in hypertension study (LIFE): a randomised trial against atenolol. Lancet. 2002;359(9311):995–1003. doi:10.1016/S0140-6736(02)08089-3Landmark LIFE trial (n=9,193); demonstrated 13% RRR in composite endpoint and 25% stroke risk reduction with losartan vs atenolol in HTN with LVH.
- Brenner BM, Cooper ME, de Zeeuw D, et al. Effects of losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathy. N Engl J Med. 2001;345(12):861–869. doi:10.1056/NEJMoa011161RENAAL trial (n=1,513); established losartan’s renoprotective benefit with 16% reduction in composite renal endpoint and 28% ESRD risk reduction in T2DM nephropathy.
- Kjeldsen SE, Dahlof B, Devereux RB, et al. Effects of losartan on cardiovascular morbidity and mortality in patients with isolated systolic hypertension and left ventricular hypertrophy: a LIFE substudy. JAMA. 2002;288(12):1491–1498. doi:10.1001/jama.288.12.1491LIFE substudy demonstrating 25% composite endpoint reduction in isolated systolic hypertension with LVH, including 46% reduction in CV mortality.
- Lindholm LH, Ibsen H, Dahlof B, et al. Cardiovascular morbidity and mortality in patients with diabetes in the Losartan Intervention For Endpoint reduction in hypertension study (LIFE). Lancet. 2002;359(9311):1004–1010. doi:10.1016/S0140-6736(02)08090-XLIFE diabetic substudy showing significant reductions in total and CV mortality favouring losartan over atenolol in hypertensive diabetics with LVH.
- Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults. J Am Coll Cardiol. 2018;71(19):e127–e248. doi:10.1016/j.jacc.2017.11.006US hypertension guideline positioning ARBs as first-line agents for compelling indications including LVH, CKD, and diabetes.
- Heidenreich PA, Bozkurt B, Aguilar D, et al. 2022 AHA/ACC/HFSA guideline for the management of heart failure. Circulation. 2022;145(18):e895–e1032. doi:10.1161/CIR.0000000000001063Supports ARBs as alternatives to ACE inhibitors in ACEi-intolerant HFrEF patients; relevant to off-label losartan use in heart failure.
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117–S314. doi:10.1016/j.kint.2023.10.018Updated CKD guideline recommending RAAS blockade (ACEi or ARB) in patients with diabetes and albuminuria for renoprotection.
- Devereux RB, Dahlof B. Potential mechanisms of stroke benefit favoring losartan in the LIFE study. Curr Med Res Opin. 2007;23(2):443–457. doi:10.1185/030079906X167435Explores mechanisms behind losartan’s stroke benefit including LVH regression, atrial fibrillation prevention, uric acid reduction, and anti-thrombotic effects.
- Mulla S, Siddiqui WJ. Losartan. In: StatPearls. Treasure Island (FL): StatPearls Publishing; Updated February 26, 2024. NCBI BookshelfComprehensive pharmacology review covering mechanism, pharmacokinetics, clinical indications, and adverse effects of losartan.
- Sica DA, Gehr TWB, Ghosh S. Clinical pharmacokinetics of losartan. Clin Pharmacokinet. 2005;44(8):797–814. doi:10.2165/00003088-200544080-00003Detailed PK review covering CYP2C9/3A4 metabolism, EXP3174 formation, hepatic/renal impairment effects, and drug-drug interaction profile.
- Lo MW, Goldberg MR, McCrea JB, et al. Pharmacokinetics of losartan, an angiotensin II receptor antagonist, and its active metabolite EXP3174 in humans. Clin Pharmacol Ther. 1995;58(6):641–649. doi:10.1016/0009-9236(95)90020-9Foundational PK study in 18 healthy subjects characterising oral bioavailability (~33%), clearance (610 mL/min), Vd (34 L), and active metabolite kinetics.