ACE inhibitors and ARBs lower blood pressure about equally, and both are recommended as first-line treatments for hypertension, but they are not interchangeable in every clinical situation. The differences that matter most show up in side effects, mortality outcomes in specific conditions, and tolerability. Which class a doctor chooses for you depends less on how well either one controls blood pressure and more on what else is going on with your health.
How They Work Differently
Both drug classes target the same hormonal system that raises blood pressure, but they interrupt it at different points. ACE inhibitors block the enzyme that converts angiotensin I into angiotensin II, a hormone that tightens blood vessels. ARBs take a different approach: they let angiotensin II form normally but block it from latching onto its receptor (called AT1) in blood vessel walls, so the hormone can’t do its job.1PubMed Central. Angiotensin II receptor blockers
That difference might sound like a technicality, but it has real consequences. The enzyme that ACE inhibitors block also breaks down bradykinin, a substance that widens blood vessels and triggers inflammation. When an ACE inhibitor stops this enzyme from working, bradykinin builds up. The enzyme actually has a higher affinity for bradykinin than for angiotensin I, which means ACE inhibitors may be even better at raising bradykinin levels than they are at stopping angiotensin II production.2PubMed. Unraveling the Pivotal Role of Bradykinin in ACE Inhibitor Activity That extra bradykinin is thought to provide some cardiovascular benefit, but it’s also the reason ACE inhibitors cause a dry cough and, rarely, a dangerous swelling reaction.
Blood Pressure Lowering Is Essentially a Tie
If the only question is “which lowers blood pressure more,” the answer is neither. A systematic review comparing the two classes found that both are similar in their efficacy at reducing blood pressure.3PubMed 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 A large multinational observational study reached the same conclusion but added an important caveat: while the two classes didn’t differ significantly in effectiveness, ARBs showed a better safety profile.4Hypertension. Comparative First-Line Effectiveness and Safety of ACE (Angiotensin-Converting Enzyme) Inhibitors and Angiotensin Receptor Blockers: A Multinational Cohort Study A separate analysis looking at not just blood pressure but also hard outcomes like death, heart attack, stroke, heart failure, and kidney failure found no difference between the two classes on any of those measures.5PubMed. Angiotensin-Converting Enzyme Inhibitors in Hypertension: To Use or Not to Use?
So if someone is starting treatment for straightforward high blood pressure and tolerates both classes well, there’s no strong reason to prefer one over the other for blood pressure control alone. The real differences emerge when you look at specific outcomes in specific patient groups.
Where ACE Inhibitors May Have a Mortality Edge
The most consequential difference between these two drug classes is in their effect on death rates. When compared against placebo or other active treatments in randomized trials, ACE inhibitors have consistently reduced all-cause mortality, while ARBs have not. A meta-analysis highlighted by an Egyptian cardiology consensus found that the overall mortality benefit of blocking the renin-angiotensin system came entirely from ACE inhibitors, which were linked to about a 10% reduction in all-cause mortality. ARBs showed no such reduction.6PubMed Central. ACE Inhibitors and Angiotensin Receptor Blockers for the Primary and Secondary Prevention of Cardiovascular Outcomes – Section: VI. Effects of ACEis and ARBs on Mortality
In people with diabetes, the pattern held. A meta-analysis published in JAMA Internal Medicine found that ACE inhibitors cut all-cause mortality by about 13%, cardiovascular deaths by 17%, and major cardiovascular events by 14%, including a roughly one-fifth reduction in heart attacks. ARBs didn’t significantly affect mortality or cardiovascular events in the same population, with one exception: they did reduce heart failure hospitalizations by about 30%.7JAMA Internal Medicine. Effect of Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers on All-Cause Mortality, Cardiovascular Deaths, and Cardiovascular Events in Patients With Diabetes Mellitus: A Meta-analysis
This is worth putting in context. Most of the mortality trials for ACE inhibitors were placebo-controlled, meaning they compared the drug against nothing. Head-to-head comparisons of ACE inhibitors versus ARBs show a less dramatic picture, as covered in the sections below. Still, the placebo-controlled data give ACE inhibitors a more robust evidence base for preventing death, and that carries weight in guidelines.
Heart Failure and Post-Heart-Attack Recovery
In heart failure, ACE inhibitors have been the standard-bearers for decades. A meta-analysis of randomized trials in heart failure patients found that ACE inhibitors reduced all-cause mortality by about 11% and cardiovascular deaths by about 14%. ARBs did not show a significant mortality benefit in the same analysis.8PubMed Central. Effect of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers on cardiovascular events in patients with heart failure: a meta-analysis of randomized controlled trials However, when ACE inhibitors were compared directly against ARBs in head-to-head trials of heart failure patients, neither class was clearly superior for preventing death. The same study noted that ACE inhibitors should still be considered first-line therapy in heart failure because of their stronger evidence base from placebo-controlled work.
After a heart attack, the story looks similar. A systematic review of head-to-head randomized trials in patients with prior heart attack or heart failure found no significant difference between the two classes for recurrence of heart attacks, heart failure hospitalizations, cardiovascular death, total mortality, or stroke. Hospitalization rates for heart failure were nearly identical: about 12.2% with ACE inhibitors and 12.5% with ARBs.9Hypertension Research. Angiotensin-converting enzyme inhibitors versus angiotensin receptor blockers in hypertensive patients with myocardial infarction or heart failure: a systematic review and meta-analysis What did differ was tolerability: patients on ACE inhibitors were about 40% more likely to stop their medication because of side effects. That finding matters in the real world, because a drug you stop taking can’t help you.
The Side Effect That Drives Most Switches
The dry, persistent cough that ACE inhibitors cause is the most common reason patients switch to an ARB. It affects roughly 2% to 11% of people taking an ACE inhibitor, depending on the study and the population.10PubMed Central. ACEI-induced cough: A review of current evidence and its practical implications for optimal CV risk reduction – Section: Magnitude of cough The cough is caused by the bradykinin buildup described earlier. Because ARBs don’t interfere with bradykinin breakdown, cough rates with ARBs are much lower.
If you stop an ACE inhibitor because of cough, the cough doesn’t vanish overnight. A prospective study tracking patients who quit enalapril found that the cough improved markedly by two weeks but could take up to four weeks to fully resolve. The underlying sensitivity of the cough reflex, measured by response to inhaled capsaicin, declined in parallel over those 28 days.11PubMed Central. Resolution of ACE inhibitor cough: changes in subjective cough and responses to inhaled capsaicin, intradermal bradykinin and substance-P
Angioedema Risk
Angioedema, a swelling of the deeper layers of the skin that can affect the throat and become life-threatening, is rare with either class but considerably more common with ACE inhibitors. A meta-analysis of randomized trials found that ACE inhibitors carried about 2.2 times the risk of angioedema compared to ARBs in head-to-head comparisons. The overall incidence was about 0.30% with ACE inhibitors versus 0.11% with ARBs, which was not significantly different from placebo.12PubMed. Meta-analysis of randomized trials of angioedema as an adverse event of renin-angiotensin system inhibitors An analysis of adverse drug reaction reports added that ACE inhibitor-associated angioedema episodes were more often rated as life-threatening compared to those associated with ARBs.13PLoS ONE. Angioedemas associated with renin-angiotensin system blocking drugs: Comparative analysis of spontaneous adverse drug reaction reports
Despite the lower risk with ARBs, prescribing an ARB to someone who had angioedema on an ACE inhibitor is still done cautiously. A small percentage of patients will develop angioedema on an ARB too, possibly through different mechanisms. But for most people who experienced ACE inhibitor angioedema, switching to an ARB is considered reasonable with monitoring.
Potassium and Kidney Function
Both ACE inhibitors and ARBs can raise potassium levels, since blocking the renin-angiotensin system reduces the hormone signal that normally helps the kidneys excrete potassium. One comparative study found that hyperkalemia was more common among ARB users than ACE inhibitor users, with ARB use associated with roughly a 40% to 55% increase in the odds of elevated potassium after adjusting for kidney function.14PubMed Central. A comparative study of the prevalence of hyperkalemia with the use of angiotensin-converting enzyme inhibitors versus angiotensin receptor blockers This finding runs counter to the general perception that ARBs have a cleaner side-effect profile in every respect. People with impaired kidney function or diabetes are at the highest risk, and monitoring potassium levels is standard practice regardless of which class you’re taking.
Kidney Protection in Diabetes
Both drug classes help protect the kidneys in people with diabetic kidney disease, but the evidence base favors them for slightly different reasons. A meta-analysis of patients with diabetic nephropathy found that ARBs significantly reduced the risk of progressing to end-stage renal disease, while ACE inhibitors showed a trend toward reduction that didn’t quite reach statistical significance. Both classes reduced the risk of doubling of serum creatinine, a marker for worsening kidney function.15American Journal of Hypertension. Effects of Renin–Angiotensin System Blockers on Renal Outcomes and All-cause Mortality in Patients With Diabetic Nephropathy: An Updated Meta-analysis Neither class affected all-cause mortality in this kidney-focused analysis. In practice, either class is used for kidney protection in diabetes, with the choice often depending on which side effects the patient can tolerate.
Why You Should Never Combine Them
It might seem logical that blocking the renin-angiotensin system at two points simultaneously would be doubly effective. It isn’t, and it’s dangerous. An early systematic review found only a small additive blood pressure effect from combining an ACE inhibitor with an ARB, but the studies were too small to detect safety signals, leading the authors to recommend against routine use of the combination.16Hypertension. Systematic Review of Combined Angiotensin-Converting Enzyme Inhibition and Angiotensin Receptor Blockade in Hypertension
Later, larger trials provided those safety signals. A quantitative review of randomized data in patients with heart failure or post-heart-attack left ventricular dysfunction found that combining ARBs with ACE inhibitors significantly increased medication discontinuation due to side effects, worsening kidney function, hyperkalemia, and dangerously low blood pressure. The risk of worsening renal function roughly doubled in heart failure patients on dual therapy.17JAMA Internal Medicine. Adverse Effects of Combination Angiotensin II Receptor Blockers Plus Angiotensin-Converting Enzyme Inhibitors for Left Ventricular Dysfunction: A Quantitative Review of Data From Randomized Clinical Trials A community-based study found hyperkalemia was about twice as common during dual therapy compared to taking either drug alone.18PubMed. Hyperkalemia and renal function during monotherapy and dual renin-angiotensin blockade in the community setting Current guidelines strongly discourage this combination.
Pregnancy Is a Hard Stop for Both
Neither ACE inhibitors nor ARBs should be taken during pregnancy. A systematic review and meta-analysis found that exposure to either class during the first trimester was associated with roughly double the odds of overall congenital malformations, with a significant increase in cardiovascular malformations, miscarriage, and stillbirth.19Pharmacology Research & Perspectives. Adverse pregnancy outcomes associated with first‐trimester exposure to angiotensin‐converting enzyme inhibitors or angiotensin II receptor blockers: A systematic review and meta‐analysis A separate meta-analysis confirmed an increased risk of major congenital malformations, cardiovascular defects, and stillbirths, and found this risk was independent of the mother having hypertension itself, since women on other blood pressure medications didn’t show the same elevated risk.20Diabetes/Metabolism Research and Reviews. Increased risk of major congenital malformations in early pregnancy use of angiotensin‐converting‐enzyme inhibitors and angiotensin‐receptor‐blockers: a meta‐analysis
With ARBs specifically, case reports document severe fetal outcomes including kidney failure, lung underdevelopment, skull abnormalities, and fetal or neonatal death, thought to result from reduced blood flow to the fetal kidneys and placenta.21PubMed Central. Use of angiotensin II receptor blocker during pregnancy: A case report – Section: Adverse effects of ARBs during pregnancy Women of childbearing age are typically advised to use effective contraception while on either class, and any woman planning pregnancy should be switched to a safer alternative well in advance.
Ethnicity and Treatment Response
There is a longstanding clinical observation that Black patients may have a reduced blood pressure response to either ACE inhibitors or ARBs when used alone, compared to white patients. A review of the evidence found that while multiple monotherapy trials supported this observation, other studies suggested race isn’t the primary predictor of response, and the difference disappears when these drugs are combined with other medications like diuretics.22PubMed. A Review of ACE Inhibitors and ARBs in Black Patients With Hypertension U.S. guidelines generally recommend that Black patients start with a calcium channel blocker or diuretic rather than an ACE inhibitor or ARB as monotherapy.
A more recent and nuanced analysis using UK clinical data compared ARBs and ACE inhibitors across ethnic groups. For a composite cardiovascular outcome, there was no significant difference between the two classes regardless of ethnicity. But when researchers looked specifically at cardiovascular-related death, a divergence appeared: white patients on ARBs had a lower risk of cardiovascular death compared to those on ACE inhibitors, while Black patients on ARBs had a higher risk of cardiovascular death compared to those on ACE inhibitors. South Asian patients showed no difference between the two classes.23PubMed Central. Effectiveness and risk of ARB and ACEi among different ethnic groups in England: A reference trial (ONTARGET) emulation analysis using UK Clinical Practice Research Datalink Aurum-linked data This is observational data, so it doesn’t prove causation, but it raises important questions about whether one-size-fits-all switching from ACE inhibitors to ARBs is appropriate across all populations.
Sticking With the Medication
Adherence data give a slight practical edge to ARBs. One study found that persistence rates over three years were similar between the two classes (about 82%), but patients on ACE inhibitors switched medications almost twice as often as those on ARBs, primarily switching to an ARB.24PubMed. Compliance, persistence, and switching patterns for ACE inhibitors and ARBs Another large study found that a slightly higher proportion of ARB patients remained persistent with their medication compared to ACE inhibitor patients, with both classes outperforming beta-blockers, calcium channel blockers, and diuretics.25The Journal of Clinical Hypertension. Effects of Initial Antihypertensive Drug Class on Patient Persistence and Compliance in a Usual‐Care Setting in the United States Compliance, meaning taking the drug as prescribed rather than just continuing to fill the prescription, was similar between the two classes.
This is relevant because a medication that patients actually keep taking delivers real-world benefits that a technically superior drug abandoned after two months does not. The higher switch rate from ACE inhibitors to ARBs, driven largely by cough, is one reason many clinicians reach for an ARB first despite the stronger mortality evidence behind ACE inhibitors.
Dementia Risk
An emerging area of research suggests ARBs may offer an advantage in protecting the brain. A study of patients with mild cognitive impairment found that those taking ARBs had roughly half the risk of progressing to dementia compared to those on ACE inhibitors.26Hypertension. Angiotensin Receptor Blockers Are Associated With a Lower Risk of Progression From Mild Cognitive Impairment to Dementia A larger retrospective cohort study found ARB users had about a 20% lower risk of developing Alzheimer’s disease and related dementias compared to ACE inhibitor users, with ARBs that cross the blood-brain barrier showing an even greater association with reduced risk.27EBioMedicine. Angiotensin II receptor blockers are associated with lower risk of Alzheimer’s disease and related dementias compared to other antihypertensive medications: a retrospective cohort study
These findings are observational, so they can’t prove ARBs actually prevent dementia. People who end up on ARBs might differ from ACE inhibitor users in ways researchers can’t fully account for. But the consistency of the signal across multiple studies and the biological plausibility (angiotensin II receptors in the brain play roles in neuroinflammation and vascular health) make this an area worth watching. It’s not yet a reason to switch your blood pressure medication on its own.
Cost Considerations
When ARBs were still under patent, they were significantly more expensive than generic ACE inhibitors, which made cost a major factor in prescribing decisions. Now that most ARBs are available as generics, the price gap has narrowed. A cost-effectiveness analysis of heart failure management found that ACE inhibitors were associated with lower overall costs and slightly better quality-adjusted life years than ARBs, though the difference was modest.28PubMed Central. Cost-effectiveness of ace inhibitors versus ARBs in heart failure management A broader systematic review of cost-effectiveness studies found ARBs were actually more cost-effective than ACE inhibitors across several analyses, though the authors cautioned that results varied widely depending on the setting and analytic approach, and are affected by changing generic drug prices.29PubMed Central. Cost-effectiveness Analyses of Antihypertensive Medicines: A Systematic Review
In kidney disease specifically, both classes were cost-saving compared to conventional treatments that don’t block the renin-angiotensin system, but direct comparisons between the two classes lacked sufficient evidence to declare a winner.30PubMed Central. Economic evaluations of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers in type 2 diabetic nephropathy: a systematic review For most patients today, cost is no longer the deciding factor between these two classes.
Uric Acid and Gout
One quirky difference between the classes involves uric acid, the substance that causes gout. The ARB losartan has a mild uricosuric effect, meaning it helps the kidneys clear uric acid from the blood. In one study, losartan decreased serum uric acid and increased its clearance, while the ACE inhibitor enalapril did not.31Internal Medicine. Effect of the Angiotensin II Receptor Antagonist Losartan on Uric Acid and Oxypurine Metabolism in Healthy Subjects This effect appears to be specific to losartan among the ARBs, rather than a class-wide property, and stems from losartan’s interaction with uric acid transporters in the kidney.32PubMed. Cardiovascular drugs and serum uric acid Some ACE inhibitors like captopril and enalapril also mildly increase uric acid excretion, but the effect is smaller. For patients with hypertension and gout or high uric acid levels, losartan can serve double duty in a way other blood pressure medications in either class can’t match.