Losartan

Losartan belongs to the angiotensin II receptor blocker (ARB) class. Like ACE inhibitors, ARBs target the renin-angiotensin-aldosterone system (RAAS), but they work at a different point in the cascade ^{[1, 6]}.

The RAAS system works as follows: When the body senses low blood pressure or reduced blood flow, the kidneys release renin, which triggers a cascade producing angiotensin II — a powerful hormone that constricts blood vessels, stimulates aldosterone release (causing salt and water retention), and promotes cardiac remodeling. This all raises blood pressure ^{[1, 6, 11]}.

While ACE inhibitors block the enzyme that creates angiotensin II, ARBs like losartan work downstream — they block the AT1 receptor, the receptor through which angiotensin II exerts most of its harmful cardiovascular effects. Angiotensin II is still produced, but it cannot act on the AT1 receptor ^{[1, 8, 11]}.

This difference has a practical benefit: because ARBs do not affect bradykinin metabolism (unlike ACE inhibitors, which increase bradykinin levels), ARBs have a dramatically lower incidence of dry cough (1-2% vs 10-15%) and angioedema ^{[1, 8]}. This makes ARBs the standard alternative for patients who cannot tolerate ACE inhibitors due to cough.

Losartan was the first ARB approved (1995) and has unique properties within its class: it is a uricosuric agent (it lowers uric acid levels by promoting uric acid excretion in the kidneys through inhibition of the URAT1 transporter), which may benefit patients with gout or hyperuricemia ^{[1, 5, 11]}. This uricosuric effect is not shared by other ARBs.

The LIFE trial demonstrated losartan's superiority over atenolol (a beta-blocker) in reducing cardiovascular events, particularly stroke, in patients with hypertension and left ventricular hypertrophy ^[2]. The RENAAL trial established losartan's benefit in slowing progression of diabetic nephropathy in patients with type 2 diabetes ^[3].

When you start losartan, blood pressure lowering begins within 1-2 hours, with peak effect at about 6 hours ^[1]. The full antihypertensive effect of a given dose takes 3-6 weeks to develop ^{[1, 6]}. Your doctor will typically start at 50 mg once daily and may increase to 100 mg if needed.

Most people tolerate losartan very well — it has one of the cleanest side effect profiles of any blood pressure medication ^{[1, 8]}. Unlike ACE inhibitors, it rarely causes cough (only 1-2% of patients, similar to placebo rates) ^{[1, 8]}. Unlike beta-blockers, it does not cause fatigue or sexual dysfunction. Unlike calcium channel blockers, it does not cause significant ankle swelling.

Dizziness may occur during the first few days, especially if you are dehydrated or taking a diuretic ^[1]. Your doctor may check your blood pressure, kidney function (creatinine), and potassium levels within 1-2 weeks of starting ^{[1, 6]}.

Losartan has an added benefit of lowering uric acid levels, which is unique among ARBs ^{[1, 5]}. This makes it a particularly good choice for patients with hypertension who also have gout or elevated uric acid.

If you are taking losartan for diabetic nephropathy, your doctor will monitor kidney function and potassium more closely, as these patients are at higher risk for hyperkalemia and acute kidney injury ^{[1, 3]}. The RENAAL trial demonstrated that losartan reduces the risk of doubling of serum creatinine by 25% and end-stage renal disease by 28% in patients with type 2 diabetic nephropathy ^[3].

Losartan can be taken with or without food. Absorption is not significantly affected by meals ^[1].

Potassium-rich foods: As with ACE inhibitors, patients on losartan should avoid excessive potassium intake and potassium-containing salt substitutes ^{[1, 6]}. Normal dietary potassium from foods is generally fine, but discuss any dietary supplements with your doctor. The risk of hyperkalemia is highest in patients with diabetes, kidney disease, or those taking potassium-sparing diuretics ^[1].

Alcohol: Alcohol can enhance the blood-pressure-lowering effect of losartan ^[1]. Moderate consumption is generally acceptable, but be aware of potential dizziness, especially when starting treatment.

Salt intake: Reducing sodium intake enhances losartan's antihypertensive effect ^{[1, 6]}. Follow your doctor's dietary recommendations. The DASH diet is complementary to ARB therapy ^[6].

NSAIDs: Concurrent use of NSAIDs (ibuprofen, naproxen, meloxicam) can reduce losartan's blood pressure-lowering effect and increase the risk of kidney injury ^{[1, 6]}. Use acetaminophen for pain when possible.

Losartan is dosed once or twice daily ^[1].

Hypertension [1, 6]: - Starting dose: 50 mg once daily (25 mg if volume-depleted or on a diuretic) - Usual range: 25-100 mg/day in one or two doses - Maximum: 100 mg/day - If BP not adequately controlled at 50 mg once daily, can increase to 100 mg or add a low-dose diuretic

Diabetic Nephropathy (type 2 diabetes with proteinuria) [1, 3]: - Starting dose: 50 mg once daily - Target: 100 mg once daily (titrate based on BP response)

Stroke Risk Reduction (hypertension with LVH) [1, 2]: - Starting dose: 50 mg once daily - May add hydrochlorothiazide 12.5 mg and/or increase losartan to 100 mg

Pediatric Hypertension (ages 6-16) [1]: - Weight 20 to <50 kg: 0.7 mg/kg (up to 50 mg) once daily - Weight >=50 kg: 50 mg once daily

Renal Dosing [1]: - No dose adjustment needed for renal impairment (including hemodialysis) - However, monitor potassium and creatinine more closely with renal impairment

Hepatic Impairment [1, 9]: - Start at 25 mg once daily (reduced conversion to active metabolite)

Monitoring [1, 6]: - Blood pressure - Serum creatinine and potassium at 1-2 weeks after initiation, then periodically - Uric acid levels may decrease (monitor if clinically relevant) ^[5]

Losartan is available as an affordable generic since 2010 ^{[1, 12]}.

Generic pricing: Generic losartan costs approximately $4-$12 per month for a 30-day supply. Available on most $4 generic lists.

Brand Cozaar: Rarely prescribed; costs $200-$350/month. No advantage over generic ^[1].

Insurance: Tier 1 on virtually all formularies. ARBs are widely accessible.

Combination products: Generic losartan/hydrochlorothiazide (Hyzaar generic) is available for patients needing dual therapy, often at similar cost to losartan alone ^[12].

Comparison to other ARBs: Generic losartan is among the cheapest ARBs. Valsartan and irbesartan are also available as affordable generics. Newer ARBs (olmesartan, azilsartan) may cost more ^[12].

Pregnancy: Losartan is CONTRAINDICATED throughout pregnancy. This is the basis of its boxed warning ^{[1, 10]}. ARBs used in the second and third trimesters cause fetal renal dysfunction, oligohydramnios, skull hypoplasia, pulmonary hypoplasia, and death — the same mechanism as ACE inhibitors. First-trimester exposure data are limited but suggest risk ^{[1, 10]}.

Women of childbearing potential must use effective contraception. Discontinue losartan immediately upon pregnancy detection. Alternative antihypertensives with established pregnancy safety profiles (labetalol, nifedipine, methyldopa) should be used instead ^{[1, 6, 10]}.

Breastfeeding: It is not known whether losartan or its active metabolite is excreted in human breast milk ^[1]. Due to the potential for serious adverse effects in nursing infants, losartan is generally not recommended during breastfeeding. ACE inhibitors with more breastfeeding safety data (captopril, enalapril) may be preferred if RAAS inhibition is needed ^[1].

Generic losartan has been available since April 2010 ^{[1, 12]}.

- Generic losartan: $4-$12/month. FDA AB-rated. Multiple manufacturers. - Brand Cozaar: $200-$350/month. Same active ingredient.

All generic losartan products are therapeutically equivalent. There is no clinical reason to use brand Cozaar ^[1].

Note on CYP2C9 metabolism [1, 9]: Losartan is converted to its active metabolite by CYP2C9. Approximately 1-3% of Caucasians and 2% of African Americans are CYP2C9 poor metabolizers, which may reduce the active metabolite formation and clinical efficacy. This is a pharmacogenomic consideration, not a generic vs. brand issue.