Lisinopril vs Losartan: Side-Effect Profile Head-to-Head

How These Two Drugs Work Differently

Lisinopril blocks angiotensin-converting enzyme (ACE), which prevents the conversion of angiotensin I to angiotensin II. That same enzyme also breaks down bradykinin, a peptide that dilates blood vessels. When ACE is inhibited, bradykinin accumulates. This accumulation explains the most distinctive side effect of the entire ACE inhibitor class: persistent dry cough 1.

Losartan takes a different approach. It blocks the angiotensin II type 1 (AT1) receptor directly, preventing angiotensin II from exerting its vasoconstrictive and aldosterone-stimulating effects. Because losartan does not inhibit ACE, it does not cause bradykinin buildup. The downstream result is a similar blood-pressure reduction with a fundamentally different adverse-event signature 2.

Both drugs suppress the RAAS. Both can cause hyperkalemia and raise serum creatinine, especially in patients with pre-existing kidney disease. The shared risks are real. The divergence lies in the bradykinin-mediated effects: cough, angioedema, and taste disturbance overwhelmingly favor losartan over lisinopril 3.

ACE Inhibitor Cough: The Side Effect That Drives Most Switches

Dry, nonproductive, persistent cough is the single most common reason patients stop taking lisinopril. Published estimates of ACE inhibitor cough vary widely. A 2006 meta-analysis in the Annals of Internal Medicine placed the incidence between 5% and 35%, with higher rates in women, nonsmokers, and patients of East Asian descent 1. The mechanism is bradykinin and substance P accumulation in the bronchial mucosa.

The cough typically starts within the first few months of treatment. It is usually worse at night. Some patients tolerate it. Many do not.

Losartan does not cause this cough. In the LIFE trial (N=9,193), cough rates in the losartan arm were comparable to placebo levels reported in other ARB trials 2. A 2001 Cochrane review confirmed that ARBs as a class produce cough at rates statistically indistinguishable from placebo, while ACE inhibitors produce it at rates 2 to 3 times higher 4. The 2017 ACC/AHA hypertension guideline explicitly recommends ARBs as an alternative for patients who develop ACE inhibitor cough 5.

If a patient on lisinopril develops a persistent cough, the standard clinical approach is straightforward: discontinue the ACE inhibitor, wait 1 to 4 weeks for the cough to resolve, and switch to losartan or another ARB. Dose conversion is not milligram-for-milligram. Lisinopril 20 mg daily is roughly equivalent in blood-pressure lowering to losartan 50 to 100 mg daily, though individual responses vary.

Angioedema: Rare but Potentially Life-Threatening

Angioedema, which involves swelling of the lips, tongue, face, or airway, occurs in approximately 0.1% to 0.7% of patients taking ACE inhibitors 6. The risk is 4 to 5 times higher in Black patients compared to non-Black patients, a disparity confirmed in ALLHAT and in post-marketing surveillance data 3. Angioedema can develop at any point during treatment, not just in the first weeks.

The mechanism, like cough, involves bradykinin. Losartan carries a much lower angioedema risk. However, the risk is not zero. Roughly 2% to 17% of patients who experienced ACE inhibitor angioedema will also develop it on an ARB, according to a 2008 review in the Journal of Allergy and Clinical Immunology 6.

The American Academy of Allergy, Asthma, and Immunology (AAAAI) recommends a 6-week washout after ACE inhibitor angioedema before starting an ARB, and initiating the ARB under medical observation 6.

Dr. Nancy Brown, then at Vanderbilt University Medical Center, wrote in a 2008 commentary: "The decision to use an ARB after ACE inhibitor angioedema requires weighing the cardiovascular benefit of RAAS blockade against a small but real cross-reactivity risk" 6.

For patients with a history of ACE inhibitor angioedema requiring ICU admission or intubation, most guidelines recommend avoiding the entire RAAS-blocker class and using a calcium channel blocker or thiazide diuretic instead.

Hyperkalemia: A Shared Risk With Important Nuances

Both lisinopril and losartan reduce aldosterone secretion, which leads to potassium retention. The clinical result is a measurable rise in serum potassium. In most healthy patients, this rise is modest (0.1 to 0.3 mEq/L). In patients with chronic kidney disease, diabetes, or concurrent potassium-sparing diuretic use, the rise can be clinically significant 7.

The ALLHAT trial reported hyperkalemia rates of 1.4% in the lisinopril arm 3. In the LIFE trial, clinically significant hyperkalemia (potassium >5.5 mEq/L) occurred in roughly 1% of losartan-treated patients 2. These rates are comparable. Neither drug offers a clear advantage here.

Practical monitoring is identical for both agents: check serum potassium and creatinine at baseline, within 1 to 2 weeks of starting or titrating, and periodically thereafter. The 2012 KDIGO guidelines recommend potassium monitoring every 4 weeks during dose adjustment in CKD patients taking any RAAS blocker 8.

Patients taking potassium supplements, trimethoprim-sulfamethoxazole, or spironolactone alongside either drug face a compounded risk. The combination of an ACE inhibitor or ARB with a mineralocorticoid receptor antagonist requires especially close monitoring. The RALES trial demonstrated the real-world consequences: after the trial's publication, hospitalizations for hyperkalemia increased by 66% in Ontario, largely due to inadequate potassium monitoring in clinical practice 7.

Renal Effects: Similar Mechanisms, Similar Concerns

Both lisinopril and losartan dilate the efferent arteriole of the glomerulus, reducing intraglomerular pressure. This effect is protective over the long term, slowing the progression of diabetic nephropathy and other proteinuric kidney diseases 9. Short term, it can cause a reversible rise in serum creatinine.

A creatinine increase of up to 30% from baseline is considered acceptable after starting either drug, per the 2012 KDIGO CKD guideline 8. A rise beyond 30% should prompt evaluation for renal artery stenosis or hypovolemia.

The RENAAL trial (N=1,513) established losartan's renal-protective effect in type 2 diabetic nephropathy, showing a 16% reduction in the composite endpoint of doubling of serum creatinine, end-stage renal disease, or death compared with placebo 9. Lisinopril has its own renal-protective data, but the RENAAL trial specifically validated losartan for this indication.

Neither drug should be used in patients with bilateral renal artery stenosis. Both are contraindicated in pregnancy.

Hypotension and Dizziness

First-dose hypotension is a known risk with both drug classes, though it is more commonly discussed with ACE inhibitors. Patients who are volume-depleted (from diuretics, vomiting, or diarrhea) are most vulnerable.

In the LIFE trial, dizziness was reported in 2.9% of losartan-treated patients versus 3.5% of atenolol-treated patients 2. The ALLHAT investigators reported symptomatic hypotension in a small percentage of the lisinopril arm, though exact rates were not a primary reported outcome 3.

Starting at lower doses and titrating slowly reduces this risk with either agent. Lisinopril is typically started at 5 to 10 mg daily for hypertension. Losartan starts at 25 to 50 mg daily. Neither drug requires dose adjustment for hepatic metabolism in most patients, though losartan's active metabolite (EXP 3174) is produced via CYP2C9, which can be relevant in patients taking fluconazole or similar CYP2C9 inhibitors 10.

Metabolic Side Effects and Uric Acid

Losartan has a unique pharmacologic property among ARBs: it lowers serum uric acid by inhibiting URAT1 in the proximal tubule 11. No other ARB does this to a clinically meaningful degree. In the LIFE trial, losartan reduced uric acid by approximately 0.3 mg/dL, and a post hoc analysis attributed roughly 29% of losartan's cardiovascular benefit to this uricosoric effect 2.

Lisinopril has no significant effect on uric acid levels.

For patients with concurrent gout or hyperuricemia, this is a clinically meaningful differentiator. The 2020 American College of Rheumatology (ACR) gout guideline conditionally recommends losartan as the preferred antihypertensive in gout patients who need RAAS blockade 11.

Neither drug worsens lipid profiles or glucose metabolism. Both are considered metabolically neutral, a significant advantage over older antihypertensives like thiazide diuretics (which can raise glucose) and beta-blockers (which can worsen lipid profiles).

What the Major Trials Tell Us About Overall Tolerability

No large randomized trial has directly compared lisinopril to losartan head-to-head. The available evidence comes from indirect comparisons across landmark trials.

ALLHAT (2002, N=33,357): The lisinopril arm showed equivalent primary cardiovascular outcomes (combined fatal coronary heart disease and nonfatal myocardial infarction) compared with the chlorthalidone arm. Black participants randomized to lisinopril had 24.1% higher stroke rates than those randomized to chlorthalidone (RR 1.40 to 95% CI 1.17 to 1.68), a finding that led to ongoing debate about ACE inhibitor efficacy in this population 3. The ALLHAT findings were influential in shaping RAAS-blocker prescribing.

LIFE (2002, N=9,193): Losartan produced a 13% relative risk reduction in the composite primary endpoint (cardiovascular death, stroke, or myocardial infarction) versus atenolol (p=0.021). Drug discontinuation due to adverse events occurred in 7.8% of the losartan group compared with 9.2% of the atenolol group 2. Stroke reduction was the main driver: losartan lowered stroke risk by 25% versus atenolol.

The 2017 ACC/AHA guideline, authored by Paul Whelton and colleagues, states: "ACE inhibitors and ARBs are both recommended as first-line agents for hypertension; the choice between them should be influenced by patient tolerance and comorbidities" 5.

In aggregate, losartan has a tolerability edge. Patients taking losartan are less likely to stop their medication because of side effects, and the placebo-subtracted adverse event rate is lower.

Special Populations: Where the Side-Effect Gap Widens

Women. ACE inhibitor cough is 2 to 3 times more common in women than in men. This disparity alone makes losartan a practical first choice for many women who need RAAS blockade 1.

Black patients. ACE inhibitor angioedema is 4 to 5 times more common in Black patients. The ALLHAT stroke data in Black participants add a separate concern. The 2014 JNC 8 panel recommended calcium channel blockers or thiazide diuretics as first-line in Black patients without CKD, with RAAS blockers reserved for those with proteinuria or diabetes 12. When RAAS blockade is needed, ARBs like losartan carry a more favorable safety profile in this population.

East Asian patients. ACE inhibitor cough incidence may reach 30% to 35% in East Asian populations, compared with 5% to 15% in White populations. Genetic variation in the bradykinin B2 receptor and ACE gene polymorphisms likely explain this difference 1.

Pregnancy. Both drugs are absolutely contraindicated in the second and third trimesters. Both can cause fetal renal agenesis, oligohydramnios, and skull ossification defects. There is no safety advantage to either agent in pregnancy.

Elderly patients. Both drugs are well tolerated in older adults. The LIFE trial enrolled patients aged 55 to 80, and losartan's tolerability advantage held across age subgroups 2.

Drug Interactions That Affect Side-Effect Risk

Both lisinopril and losartan interact with potassium-sparing diuretics, NSAIDs, and lithium. These interactions are class effects, shared by all ACE inhibitors and ARBs.

NSAIDs blunt the antihypertensive effect of both drugs and increase the risk of acute kidney injury when combined with a RAAS blocker. The "triple whammy" combination of RAAS blocker plus diuretic plus NSAID is a well-documented cause of preventable acute kidney injury 13.

Losartan has one unique interaction profile element: its conversion to the active metabolite EXP 3174 depends on CYP2C9. Fluconazole, amiodarone, and fluvoxamine can inhibit this conversion, potentially reducing losartan's efficacy without altering its parent-compound side-effect profile 10. Lisinopril is not hepatically metabolized and has no CYP-mediated interactions. It is excreted unchanged by the kidneys.

For patients on multiple interacting medications, lisinopril's lack of hepatic metabolism is an advantage. For patients prone to cough or angioedema, losartan's receptor-level mechanism is an advantage. The choice depends on which risk matters more for the individual patient.

Making the Switch: Practical Considerations

The most common clinical scenario is switching from lisinopril to losartan due to cough. The process is straightforward.

Stop lisinopril. Start losartan the next day. Cough typically resolves within 1 to 4 weeks, though some reports describe resolution taking up to 3 months in rare cases. There is no need for a washout period when switching from an ACE inhibitor to an ARB for cough (as opposed to the 6-week washout recommended after angioedema).

Dose conversion is approximate: lisinopril 10 mg corresponds roughly to losartan 50 mg, and lisinopril 20 mg to losartan 50 to 100 mg. Check blood pressure within 2 to 4 weeks of the switch and titrate as needed.

Do not combine lisinopril and losartan. The ONTARGET trial (N=25,620) showed that dual RAAS blockade with an ACE inhibitor plus an ARB increased the risk of hyperkalemia, hypotension, and renal dysfunction without improving cardiovascular outcomes 14. The FDA and the European Medicines Agency both advise against this combination.