Losartan is an ARB (angiotensin II receptor blocker), not an ACE inhibitor, and it was the first ARB ever approved.1PubMed Central. Fifteen years of losartan: what have we learned about losartan that can benefit chronic kidney disease patients The two classes are close cousins that go after the same blood-pressure hormone from different ends. They lower blood pressure about equally, so the practical difference shows up mostly in side effects.
How Losartan Works Differently From an ACE Inhibitor
Your body makes a hormone called angiotensin II that tightens blood vessels and raises blood pressure. Losartan blocks the action of substances like this, so blood flows more smoothly and the heart pumps more efficiently.2MedlinePlus. Losartan: MedlinePlus Drug Information ACE inhibitors take an earlier step: they stop angiotensin II from being formed. ARBs let it form but block it at its docking sites on blood vessels and the heart.3PubMed Central. A Review of the Role of Bradykinin and Nitric Oxide in the Cardioprotective Action of Angiotensin-Converting Enzyme Inhibitors: Focus on Perindopril
The route matters because the enzyme ACE inhibitors block also breaks down another substance, bradykinin, so ACE inhibitors let it build up.4PubMed Central. A Review of the Role of Bradykinin and Nitric Oxide in the Cardioprotective Action of Angiotensin-Converting Enzyme Inhibitors: Focus on Perindopril ARBs don’t touch that enzyme, so they don’t raise bradykinin this way.5PubMed Central. A Review of the Role of Bradykinin and Nitric Oxide in the Cardioprotective Action of Angiotensin-Converting Enzyme Inhibitors: Focus on Perindopril Side effects tied to bradykinin, like cough, are therefore expected to be less common with losartan. The vessel-tightening hormone can also be made by other routes in the body. An ARB blocking the receptor covers those routes, while an ACE inhibitor may not.
You can usually tell the classes apart by the name on the bottle. ARB generic names end in “-sartan”: losartan, valsartan, irbesartan, candesartan, telmisartan. ACE inhibitor names end in “-pril”: lisinopril, enalapril, ramipril, perindopril. Losartan’s brand name is Cozaar.
Losartan also comes paired with hydrochlorothiazide, a water pill, in one tablet sold as Hyzaar. A bottle like that lists two active ingredients, and the losartan part is the ARB. Check each ingredient separately, because the second one belongs to a different class and has its own side effects.
Does Losartan Work as Well as an ACE Inhibitor
ARBs and ACE inhibitors lower blood pressure equally well when used alone.6PubMed Central. A Comparative Study of the Safety and Efficacy Between Angiotensin-Converting Enzyme Inhibitors and Angiotensin Receptor Blockers on the Management of Hypertension: A Systematic Review In a large multinational comparison of people starting either class, rates of heart attack, heart failure and stroke were about the same.7PubMed Central. Comparative first-line effectiveness and safety of angiotensin converting enzyme inhibitors and angiotensin receptor blockers: a multinational cohort study A review of people with high blood pressure, including those with diabetes or kidney disease, found no difference in deaths, heart attacks, strokes or kidney failure.8PubMed. Angiotensin-Converting Enzyme Inhibitors in Hypertension: To Use or Not to Use?
Losartan also has its own track record. In people with type 2 diabetes and kidney damage, it cut the risk of kidney failure by about 28% compared with a dummy pill, and that benefit was larger than the blood-pressure drop alone would explain.9PubMed. Effects of losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathy In people with high blood pressure and a thickened heart muscle, losartan lowered stroke risk by about 25% compared with the beta-blocker atenolol.10PubMed. Losartan: a review of its use in stroke risk reduction in patients with hypertension and left ventricular hypertrophy Blood pressure fell about equally on both drugs, yet losartan also meant fewer new cases of diabetes.11PubMed. Losartan: in the reduction of stroke risk in patients with hypertension and left ventricular hypertrophy Because of the kidney results, losartan is commonly prescribed specifically to protect kidneys in diabetes.
For someone switching, equal effectiveness means the change from lisinopril to losartan is usually made for side effects, not because one works better. Your doctor will still recheck your blood pressure afterward to confirm the dose fits. Doses aren’t one-to-one between drugs, so never swap pills yourself.
A person who coughs on an ACE inhibitor is a typical candidate for losartan. ACE inhibitors are often tried first because they have been used longer and many are inexpensive generics, though losartan is a low-cost generic too. Existing conditions, pregnancy plans and past reactions to medicines all feed into the choice.
Cough and Swelling on Losartan Versus ACE Inhibitors
Across many trials, ACE inhibitors caused cough about 3 times as often as ARBs.12PubMed Central. Angiotensin‐converting enzyme inhibitor induced cough compared with placebo, and other antihypertensives: A systematic review, and network meta‐analysis In people who had already coughed on an ACE inhibitor, cough returned in 72% on lisinopril but 29% on losartan.13PubMed. ACE inhibitors, angiotensin II antagonists and cough. The Losartan Cough Study Group In that same group, 34% coughed on a water pill, so losartan’s rate was no higher than a drug that doesn’t touch this system.14PubMed. ACE inhibitors, angiotensin II antagonists and cough. The Losartan Cough Study Group
The ACE inhibitor cough is dry and tickly, with no mucus, and often worse at night. It can start weeks or months after you begin the pill. It usually fades within days to a few weeks of stopping, sometimes longer. If a cough persists after switching, tell your doctor, since a cold or reflux may be behind it.
ACE inhibitors can also cause angioedema, swelling of the face, lips, tongue or throat, in about 2 to 10 of every 1,000 users.15US Pharmacist. Cross-Reactivity of ACE Inhibitor–Induced Angioedema with ARBs In trials it occurred in about 0.3% of ACE inhibitor users and 0.11% of ARB users, close to the rate on a dummy pill.16PubMed. Meta-analysis of randomized trials of angioedema as an adverse event of renin-angiotensin system inhibitors So swelling is uncommon on both classes. But ARB swelling is rare, not impossible, and a person who has had it on an ACE inhibitor should still watch for it after switching. It can begin at any time, even after years on a drug that was tolerated well, so a long clean history doesn’t rule it out.
Stopping the ACE inhibitor ended the swelling completely in only about 69% of people who had it, and 15% saw no improvement.17JAMA Internal Medicine. Angioedema Associated With Angiotensin-Converting Enzyme Inhibitor Use: Outcome After Switching to a Different Treatment Many doctors do move people to an ARB after ACE swelling, but carefully, and some choose a different class entirely after severe swelling.
Trouble breathing, a thick-feeling tongue or a tight throat calls for emergency help on any of these drugs, not a call to the office to wait for a reply.18PubMed. Meta-analysis of randomized trials of angioedema as an adverse event of renin-angiotensin system inhibitors Mild lip puffiness that comes and goes should still be reported the same day, because it can be an early sign of a larger episode.
Why Losartan and an ACE Inhibitor Shouldn’t Be Taken Together
Blood-pressure guidelines advise against combining an ACE inhibitor with an ARB.19PubMed Central. Dual Blockade of the Renin-angiotensin-aldosterone System in Type 2 Diabetic Kidney Disease A large trial found no extra protection from deaths or heart events, but more high potassium, dizziness from low pressure and kidney decline.20PubMed Central. Dual Blockade of the Renin-angiotensin-aldosterone System in Type 2 Diabetic Kidney Disease A trial of losartan plus lisinopril in diabetic kidney disease was stopped early for safety.21PubMed Central. Dual Blockade of the Renin-angiotensin-aldosterone System in Type 2 Diabetic Kidney Disease In kidney disease, combining raised high-potassium risk by about 1.8 times and low pressure by about 2.4 times.22PubMed Central. Efficacy and safety of dual vs single renin–angiotensin–aldosterone system blockade in chronic kidney disease
Pushing blood pressure and kidney filtering down further is what causes the dizziness and kidney decline, so the harms add up without a matching benefit. The only exception would be a specialist’s deliberate decision, so never combine the two on your own.
Doubling up usually happens by accident during a switch. Old lisinopril bottles stay in the cabinet, and a hospital or second doctor may restart the old pill without knowing. Ask the pharmacist to remove the old drug from your profile, and bring all your bottles to appointments so the list stays accurate.
Signs that a combination or dose is too strong include dizziness or faintness when standing up, and making much less urine than usual. Unusual weakness or an irregular heartbeat can signal high potassium. Call your doctor promptly if any of these appear.
Safety Rules That Apply to Losartan Just as to ACE Inhibitors
Both classes tend to raise potassium in the blood and lower the kidneys’ filtering rate.23PubMed. ACE inhibitors and ARBs: Managing potassium and renal function Both ease the pressure inside the kidney’s filters, which is helpful long term but can briefly lower filtering after a start or dose change. The same action reduces potassium loss in urine, which is why potassium can creep up, particularly with existing kidney disease.
Expect a blood test within a few weeks of starting or changing the dose. It’s a simple draw that checks potassium and creatinine, from which “eGFR,” an estimate of how well your kidneys filter, is calculated. A small eGFR dip after starting is common and expected. A large drop or a high potassium may mean a dose change. Vomiting or diarrhea can worsen both, so ask whether to pause the pill when you’re sick.
Potassium is a mineral that keeps the heart rhythm and muscles working, and too much in the blood can disturb the heartbeat. Ask before using potassium supplements or salt substitutes made with potassium. Many salt substitutes replace sodium with potassium chloride, so someone cutting salt can unknowingly take in a lot. Ordinary foods like bananas and potatoes are usually fine with healthy kidneys, but ask your doctor if your kidneys are weak or your last potassium was high.
Pregnancy needs a firm rule. Taken in the second and third trimesters, losartan can injure or even kill a developing baby.24U.S. Food and Drug Administration. COZAAR (losartan potassium) tablets It lowers the baby’s blood pressure and kidney blood flow, reducing the fluid around it.25PubMed Central. Use of angiotensin II receptor blocker during pregnancy Problems can include kidney failure, poorly developed lungs and skull, and stiff limbs.26Childhood Kidney Diseases. Angiotensin receptor blocker induced fetopathy: two case reports and literature review Exposure limited to the first trimester appears to carry much less risk, though that evidence is less certain.27U.S. Food and Drug Administration. COZAAR (losartan potassium) tablets
Stop losartan and call your doctor as soon as you know you are pregnant, and discuss alternatives before trying to conceive. If you find out early, don’t panic. Stop the drug and contact your doctor that day. They will switch you to a pregnancy-safe blood-pressure medicine, and may offer ultrasound follow-up.
Losartan With Painkillers and Other Medicines
Anti-inflammatory painkillers like naproxen, diclofenac or indomethacin can weaken losartan’s blood-pressure effect in some people.28Consensus Academic Search Engine. Losartan And NSAID Interactions Occasional use is usually fine, but ask before taking them regularly. Acetaminophen is often the gentler choice, since it doesn’t affect the kidneys or blood pressure the same way. Dehydration plus an anti-inflammatory painkiller plus losartan is a particularly hard combination on the kidneys, so be careful when sick.
Tell the pharmacist you take losartan whenever you buy pain or cold remedies. Many cold medicines contain ibuprofen or decongestants that can raise pressure. Drugs that speed up liver enzymes can make losartan wear off faster, while certain antifungals and stomach drugs that were tested haven’t caused meaningful problems.
Losartan also depends on your liver, which converts part of each dose into a stronger active form.29Clinical Therapeutics / Drugs. Losartan Potassium: Therapeutic Insights and Pharmacokinetics People with liver disease build up higher levels and may need a lower dose.30Clinical Therapeutics / Drugs. Losartan Potassium: Therapeutic Insights and Pharmacokinetics31PubMed. Role of CYP2C9 polymorphism in losartan oxidation32PubMed. Genetic variations of CYP2C9 in 724 Japanese individuals and their impact on the antihypertensive effects of losartan33Clinical Therapeutics / Drugs. Losartan Potassium: Therapeutic Insights and Pharmacokinetics
If losartan seems not to work, home readings that stay high after several weeks are worth reporting. Missed doses and anti-inflammatory painkillers are far more common explanations than genes, and genetic testing isn’t routine for losartan. Your doctor may raise the dose, add a water pill, or try another ARB.
A Side Benefit Unique to Losartan
Losartan helps the kidneys flush out uric acid, lowering its level in the blood.34PubMed. Uricosuric action of losartan via the inhibition of urate transporter 1 (URAT 1) in hypertensive patients This is one of the effects not shared by all ARBs,35PubMed Central. Fifteen years of losartan: what have we learned about losartan that can benefit chronic kidney disease patients so switching from losartan to another ARB may remove it.
High uric acid causes gout attacks in joints like the big toe. Some water pills raise uric acid, so losartan can offset that. The effect is modest, comes along with the blood-pressure treatment, and doesn’t replace gout medicine. If you have gout or high uric acid, ask whether losartan is a good fit. Your doctor can check uric acid on routine blood work.