Losartan

Cozaar

Losartan (Cozaar) is a longevity & bioregulators research compound. Angiotensin II receptor blocker. Uniquely among ARBs it's also uricosuric — it lowers uric acid, which is a genuine advantage for anyone whose diuretic or diet pushes urate up.

How Losartan works

Angiotensin II receptor blocker. Uniquely among ARBs it's also uricosuric — it lowers uric acid, which is a genuine advantage for anyone whose diuretic or diet pushes urate up.

Proposed benefits

Researched for mitochondrial and cellular-energy support, tissue-specific bioregulation and healthy-aging pathways.

Where to get Losartan

The evidence for Losartan

Graded by what exists behind each claim.

✅ Clinically validated

• Approved with large outcome trials. LIFE (9,193 patients) compared it against atenolol in hypertension with left ventricular hypertrophy and showed fewer strokes despite similar blood pressure reduction. RENAAL showed reduced progression of diabetic nephropathy.
• A trial in Marfan syndrome tested it against atenolol for aortic root dilation, on the TGF-beta rationale, and found no clear superiority — a worthwhile example of a mechanistically elegant hypothesis not carrying through.

📊 Correlative data

• Very wide prescribing. No cough, which is its main practical advantage over ACE inhibitors and the usual reason for a switch.
• It has a mild uricosuric effect — unique among ARBs — which makes it the preferred choice in someone with gout, a small but genuinely useful detail.

🧪 Theoretical / extrapolated

• Blocks the angiotensin II type 1 receptor rather than the enzyme that makes angiotensin II.
• Blocking downstream instead of upstream is the whole design difference. Bradykinin is not affected, so no cough. Angiotensin II still rises and can act on the AT2 receptor, which may itself be beneficial.
• It is a prodrug converted by CYP2C9 to a metabolite roughly ten to forty times more potent — which predicts variable response in people with reduced CYP2C9 activity.

How to read these tiers: they say how much human evidence exists, not how well something works — and ✗ flags harm, never a disappointing trial. How the evidence tiers work →

What Losartan actually does

Losartan blocks a receptor. That one word is the whole difference between this drug and an ACE inhibitor, and everything practical about it falls out of the word. Angiotensin-converting enzyme has a second job — it is also kininase II, the enzyme that destroys bradykinin — so blocking the enzyme raises bradykinin and that is where the ACE-inhibitor cough comes from. Losartan leaves the enzyme running and blocks the angiotensin II type 1 (AT1) receptor instead. Bradykinin is never touched.

The consequence the label states outright is that angiotensin II does not fall — it rises. Removing the negative feedback causes a doubling to tripling of plasma renin activity and a consequent rise in angiotensin II plasma concentration U.S. Food and Drug Administration 2025. Losartan and its metabolite have about 1000-fold greater affinity for AT1 than for AT2 U.S. Food and Drug Administration 2025, so all that extra angiotensin II has nowhere to go except the AT2 receptor, which is left wide open. Whether standing on the AT2 accelerator is good, bad or nothing is genuinely unsettled — but it is a real pharmacological difference from an ACE inhibitor, not a talking point.

There are two drugs in the tablet, and the second one is the one that works at trough. About 14% of an oral dose is converted by CYP2C9 and CYP3A4 to the carboxylic acid metabolite EXP3174, which is 10 to 40 times more potent by weight than the parent U.S. Food and Drug Administration 2025. And the two block the receptor by different kinetics. Losartan is a competitive, surmountable antagonist: pile on enough angiotensin II and you displace it. The label calls the metabolite a reversible, non-competitive inhibitor U.S. Food and Drug Administration 2025 — the insurmountable kind, which a surge of agonist cannot outcompete because it comes off the receptor too slowly. Vanderheyden 1999 is the pharmacology that separated those two behaviors experimentally, in CHO-K1 cells expressing the human AT1 receptor: losartan produced a parallel rightward shift of the angiotensin II curve, which is the signature of a surmountable antagonist, while pre-incubation with candesartan lowered the maximum inositol phosphate response, which is what insurmountable means. Practical reading: a morning adrenergic surge can overcome the parent and cannot easily overcome the metabolite, so the quality of blockade you have at 7am depends on how well you convert.

The uricosuric arm is losartan’s alone, it belongs to the parent, and it is a completely separate transporter. URAT1 (SLC22A12) is the apical urate–anion exchanger in the proximal tubule — the reabsorption pump that probenecid and benzbromarone block. Hamada 2008 showed losartan inhibits it: in hypertensive patients losartan significantly lowered serum urate with a concomitant rise in the urate/creatinine clearance ratio, while candesartan did not alter either. Two ARBs, same receptor blockade, opposite effect on urate — which is proof the urate effect is not AT1 blockade at all. It is a second, off-target activity of one molecule in the class.

Cell, rodent, human — and where it stops

Step one, in cells with a human receptor in them. Vanderheyden 1999 used CHO-K1 cells expressing human AT1 receptors to sort selective AT1 antagonists into surmountable and insurmountable classes. No animal, no disease — just the receptor kinetics that explain why the metabolite carries the effect between doses.

Step two, human pharmacokinetics, healthy volunteers, oral. Lo 1995 characterized losartan and EXP3174 in people; the numbers the label carries from that work are systemic bioavailability ~33%, ~14% conversion to the active metabolite, peak concentrations at 1 hour for the parent and 3–4 hours for the metabolite, and terminal half-lives of about 2 hours and 6–9 hours U.S. Food and Drug Administration 2025.

Step three, the outcome trial that made the drug, and the result inside it that is easy to miss. Dahlöf 2002 — LIFE — randomized 9,193 people aged 55–80 with sitting blood pressure 160–200/95–115 mm Hg and left ventricular hypertrophy on ECG, to losartan-based or atenolol-based treatment. The primary composite occurred in 508 losartan versus 588 atenolol patients (relative risk 0.87, 95% CI 0.77–0.98, p = 0.021). Almost all of it was stroke: 232 versus 309 (RR 0.75, 0.63–0.89, p = 0.001). Myocardial infarction went the other way and was not significant — 198 versus 188 (RR 1.07, p = 0.491). And here is the part that matters: blood pressure fell 30.2/16.6 mm Hg on losartan and 29.1/16.8 mm Hg on atenolol. The stroke difference was not a blood-pressure difference.

Step four, the kidney trial. Brenner 2001 — RENAAL — randomized 1,513 patients with type 2 diabetes and nephropathy to losartan 50 to 100 mg once daily or placebo on top of conventional antihypertensives. The primary composite of doubling of serum creatinine, end-stage renal disease or death was reached by 327 on losartan versus 359 on placebo — a 16% risk reduction, p = 0.02 — with sustained doubling of creatinine down 25% U.S. Food and Drug Administration 2025.

Step five, the elegant hypothesis that failed, which is why this page trusts the two above. Angiotensin II signaling drives TGF-β, TGF-β drives aortic-root dilatation in Marfan syndrome, and losartan fixed it in mice. Lacro 2014 then randomized 608 people aged 6 months to 25 years with Marfan syndrome to losartan or atenolol for 3 years. The baseline-adjusted rate of change in aortic-root z score was −0.139 ± 0.013 on atenolol and −0.107 ± 0.013 on losartan per year — P = 0.08, no difference. A mechanism can be right in a mouse, right in the signaling diagram, and still not beat a beta-blocker in a person.

The obstacle, stated exactly. Every number above was generated in someone selected for being at risk — ECG left ventricular hypertrophy in LIFE, established diabetic nephropathy in RENAAL. Absolute benefit from any blood-pressure drug scales with baseline risk, so none of it transfers arithmetically to a 35-year-old taking 25 mg for arterial stiffness or for a longevity thesis. The second obstacle is upstream of all of it: the effect depends on a CYP2C9-dependent conversion step, the label records that subjects who fail to make the metabolite carry a specific, rare defect in cytochrome P450 2C9 U.S. Food and Drug Administration 2025, and no outcome trial of this drug ever genotyped anybody.

Losartan pharmacokinetics — how much of it actually gets in

Route: oral, and two thirds of the tablet never reaches the circulation — which is the point rather than a flaw. Systemic bioavailability is about 33%, and roughly 14% of the dose comes out the other side of the liver as the active metabolite U.S. Food and Drug Administration 2025. The first-pass loss is the same first pass that does the activating, so an oral bioavailability figure understates the pharmacology here in a way it does not for most drugs.

What degrades it, and what makes it. The same two enzymes: cytochrome P450 2C9 and 3A4 carry out the biotransformation to the carboxylic acid metabolite U.S. Food and Drug Administration 2025. That is the interaction surface — a CYP2C9 inhibitor such as fluconazole, or an inducer such as rifampin, changes how much active drug you actually have, and the label describes a rare CYP2C9 defect in people who do not convert at all. Excretion is split: about 4% of an oral dose appears unchanged in urine and about 6% as the active metabolite, with roughly 35% recovered in urine and 60% in feces U.S. Food and Drug Administration 2025. Plasma protein binding is high on both — free fractions of 1.3% for losartan and 0.2% for the metabolite.

The arithmetic that explains once-daily dosing, done out loud. The parent has a terminal half-life of about 2 hours and a total plasma clearance of about 600 mL/min. The metabolite has a half-life of 6–9 hours and a clearance of about 50 mL/min — twelve times slower U.S. Food and Drug Administration 2025. Run that forward across a 24-hour dosing interval and the parent is gone after roughly ten of its half-lives while the metabolite has been through three to four of its own. What is blocking your AT1 receptors the morning after a dose is almost entirely EXP3174, which is also the insurmountable one. The kinetics and the pharmacology point at the same conclusion: this drug is only as good at trough as your conversion step is.

The oral barrier and the missing comparator. There is no injectable, subcutaneous or transdermal losartan with published pharmacokinetics, so nothing here is bypassable — the gastrointestinal route and hepatic first-pass metabolism are the entire delivery story, and peak concentrations arrive at 1 hour and 3–4 hours respectively U.S. Food and Drug Administration 2025. Renal clearance is 75 mL/min for losartan and 25 mL/min for the metabolite, which is why the label does not require a dose reduction for ordinary renal impairment: the kidney is not the main exit.

What would have to be true, and how you would know it was not

Four predictions. The first two are the ones with a lab test attached, and the last two argue against the way this drug is actually used outside a clinic.

1. Potassium and creatinine both rise once, then plateau. Draw a Comprehensive Metabolic Panel (CMP) before starting and again at 1–2 weeks. Less angiotensin II at AT1 means less aldosterone, so less potassium excreted; and angiotensin II is what constricts the efferent glomerular arteriole, so removing it drops filtration pressure and nudges creatinine up. A small step that settles is the drug working. A potassium that keeps climbing, or a creatinine that rises more than about a quarter above baseline and keeps going, is the mechanism running too hard — usually because of volume depletion, an NSAID, a potassium supplement or undiagnosed renal artery stenosis.

2. Uric acid should fall, and nothing else in this class predicts that. Draw uric acid at baseline and at 4 weeks. Hamada 2008 found losartan lowered serum urate with a rise in the urate clearance ratio while candesartan did nothing, so this is a losartan-specific URAT1 effect and not an ARB effect. It is the single cleanest falsification test on the page: if urate is flat at 4 weeks on a full dose, either the tablet is not being absorbed or the URAT1 story does not apply to you. Hold diet, alcohol and any thiazide constant across the window, because all three move urate harder than this will.

3. The prediction that cuts against once-daily 50 mg: your trough is worse than your peak, and you can measure it in a week. Parent half-life 2 hours, metabolite 6–9 U.S. Food and Drug Administration 2025. Take home blood pressure twice a day for seven consecutive days — once about 4 hours after the dose and once in the hour before the next one — and compare the averages. If the pre-dose reading is materially higher, the answer the kinetics support is splitting the dose or moving to a longer-acting ARB, not adding milligrams to one morning tablet. Note that LIFE titrated to effect and used hydrochlorothiazide on top; it was not a trial of 50 mg alone Dahlöf 2002.

4. The prediction that cuts against the longevity framing: nothing metabolic should move at all. Losartan has no lipid mechanism, no insulin-sensitizing mechanism and no anti-inflammatory mechanism — that is telmisartan’s page, not this one. So ApoB and hs-CRP at baseline and 12 weeks should be unchanged. If they move, the cause is something else you changed, and attributing it to the ARB is how a person ends up believing a blood-pressure drug is doing work it has never been shown to do. In LIFE itself, myocardial infarction was numerically higher on losartan (198 versus 188, p = 0.491); the benefit that trial actually bought was stroke Dahlöf 2002.

What nobody has tested yet

Nobody has ever genotyped CYP2C9 in a losartan outcome trial. The label names a rare CYP2C9 defect that stops the conversion entirely U.S. Food and Drug Administration 2025, the metabolite is 10–40 times more potent than the parent, and the metabolite is what is present at trough. If poor converters exist — and the label says they do — then some fraction of the 9,193 people in LIFE were taking a weak, surmountable antagonist with a 2-hour half-life and were counted as treated. The experiment is a few hundred people on a stable dose with a trough EXP3174 concentration and a CYP2C9 genotype, asking whether blood-pressure response tracks metabolite exposure better than it tracks milligrams. It has never been run.

Nobody has tested losartan against gout flares. It inhibits URAT1, which is the transporter the uricosuric gout drugs hit, and it lowers serum urate in hypertensive patients Hamada 2008. What does not exist is a randomized trial with flare count as the endpoint. That trial is cheap and obvious — hypertensive people with gout, losartan against any other ARB, flares over twelve months — and its absence is why the urate effect is described everywhere as a nice extra rather than as a treatment.

Nobody knows what the low doses do. LIFE and RENAAL used 50 to 100 mg. The 25 mg tablet exists as a cautious starting dose in people at risk of hypotension, not because any outcome was ever demonstrated at it. Whether 25 mg produces the urate effect, or adequate trough AT1 blockade, has not been measured — and both are measurable in an afternoon.

And the AT2 question, which is the one nobody can currently run. Plasma renin doubles to triples and angiotensin II rises on an ARB U.S. Food and Drug Administration 2025, so AT2 occupancy goes up on this drug and down on an ACE inhibitor. That is the single largest mechanistic difference between the two classes and there is no clinical assay for AT2 signaling in a living person, so it has never been measured in either direction. It is the reason the ARB-versus-ACE-inhibitor argument is still argued.

Losartan — its own safety story, not its class's

The boxed warning is the whole first paragraph, and it is not a class formality. “When pregnancy is detected, discontinue COZAAR as soon as possible. Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus” U.S. Food and Drug Administration 2025. Fetal renal function depends on angiotensin II; blocking it in the second and third trimester causes oligohydramnios, skull hypoplasia and renal failure. Anyone who could become pregnant needs that sentence before any of the rest of this page.

The cough numbers, with the study design attached, because without it they are misleading. The label reports two prospective double-blind randomized trials run specifically in hypertensive patients who had already had cough on an ACE inhibitor. Cough was reported in 17% on losartan, 69% on lisinopril and 25% on hydrochlorothiazide in one; 29%, 62% and 35% on placebo in the other U.S. Food and Drug Administration 2025. Read the placebo column: a quarter to a third of a cough-selected population coughs on nothing. The correct conclusion is that losartan is indistinguishable from a diuretic and from placebo, not that it causes cough in one in five people.

Hyperkalemia and the creatinine rise are the two real ones, and they are mechanism rather than toxicity. Both follow directly from AT1 blockade — aldosterone withdrawal for potassium, efferent arteriolar dilatation for creatinine — and both are why the label says to monitor serum potassium periodically U.S. Food and Drug Administration 2025. The risk multiplies with a potassium-sparing diuretic, a potassium supplement, a salt substitute (which is potassium chloride), an NSAID, or reduced kidney function. In RENAAL the population already had diabetic nephropathy, so the trial that proves the benefit was run in exactly the people in whom the potassium risk is highest Brenner 2001.

What is not this drug’s risk, and what is uniquely its own. It is not telmisartan: there is no PPAR-γ activity here, so nothing on this page carries a glitazone-style fluid-retention or weight signal. What is its own is the conversion step — alone among the common ARBs, losartan’s effect depends on CYP2C9 and CYP3A4 U.S. Food and Drug Administration 2025, so an azole antifungal, rifampin or a CYP2C9 variant changes the drug you are actually taking. And its own again is the urate effect: helpful in gout, but it means a rising urate on losartan is a genuine signal that something has changed, where on another ARB it would be noise.

Sources read for this page

• U.S. Food and Drug Administration. COZAAR (losartan potassium) tablets, for oral use - full prescribing information (NDA 020386).. FDA approved labeling, revision 2025
• Dahlöf B. Cardiovascular morbidity and mortality in the Losartan Intervention For Endpoint reduction in hypertension study (LIFE): a randomised trial against atenolol.. Lancet 2002 · PMID 11937178
• Brenner BM. Effects of losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathy.. N Engl J Med 2001 · PMID 11565518
• Hamada T. Uricosuric action of losartan via the inhibition of urate transporter 1 (URAT 1) in hypertensive patients.. Am J Hypertens 2008 · PMID 18670416
• Lacro RV. Atenolol versus losartan in children and young adults with Marfan's syndrome.. N Engl J Med 2014 · PMID 25405392
• Lo MW. Pharmacokinetics of losartan, an angiotensin II receptor antagonist, and its active metabolite EXP3174 in humans.. Clin Pharmacol Ther 1995 · PMID 8529329
• Vanderheyden PM. Distinction between surmountable and insurmountable selective AT1 receptor antagonists by use of CHO-K1 cells expressing human angiotensin II AT1 receptors.. Br J Pharmacol 1999 · PMID 10193788

Losartan — safety, from the human record

Losartan — interference & stacking

Bloodwork to run alongside Losartan

Baseline first, then again at 8–12 weeks.

The Longevity Baseline panel covers these in one order — 13 markers, $219.10 with the discount applied.

Check results you already have → · All 103 markers A–Z

Losartan — frequently asked questions

What Losartan is used for

Losartan appears under 2 goals in the goal router.

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