Does losartan cause inflammation in the body? Unpacking its Anti-Inflammatory Effects and Adverse Reactions

October 10, 2025 •

4 min read

While losartan is primarily known for treating high blood pressure by blocking the hormone angiotensin II, many people question: "Does losartan cause inflammation in the body?". In fact, scientific evidence suggests that losartan often has beneficial anti-inflammatory effects, though some specific adverse reactions may be mistaken for inflammation.

Quick Summary

Losartan is primarily known for its anti-inflammatory and anti-fibrotic properties, not for causing widespread inflammation. Certain rare side effects, such as allergic reactions or muscle pain, are distinct from systemic inflammatory processes, which the drug may help reduce. Understanding its mechanism clarifies its role in modulating inflammation.

Key Points

Losartan is an ARB: Losartan works as an Angiotensin II Receptor Blocker (ARB) to lower blood pressure and has recognized anti-inflammatory effects.
Reduces Inflammatory Markers: Studies have shown that losartan can decrease the levels of pro-inflammatory cytokines like TNF-α and IL-1β in certain contexts.
Adverse Effects are Distinct: Swelling from angioedema, muscle aches, and rash are specific side effects and not the same as widespread inflammation caused by the drug.
Protects Against Fibrosis: In addition to anti-inflammatory properties, losartan provides anti-fibrotic benefits, particularly in the kidneys and heart.
Better Tolerated than ACE Inhibitors: Losartan is often prescribed to patients who cannot tolerate ACE inhibitors due to a bothersome cough or angioedema.
Consult a Physician: Any perceived inflammatory symptoms while on losartan should be discussed with a doctor to determine the cause and appropriate management.

The Misconception: Losartan as an Inflammatory Agent

The question "Does losartan cause inflammation in the body?" stems from various factors. Some patients may experience side effects such as joint aches or muscle pain, which can be perceived as inflammatory. The most serious, albeit rare, adverse reaction is angioedema, a severe swelling that is a form of allergic reaction and can appear to be an inflammatory event. However, these are localized adverse events and not a sign that the medication's primary mechanism causes systemic inflammation. In fact, research points to the opposite conclusion, highlighting losartan's significant anti-inflammatory and anti-fibrotic capabilities.

Losartan's Mechanism and Anti-Inflammatory Effects

Losartan is an angiotensin II receptor blocker (ARB) that works by blocking the action of angiotensin II. Angiotensin II is a hormone that constricts blood vessels and promotes inflammation and fibrosis. By blocking its binding to type 1 receptors (AT1), losartan prevents these pro-inflammatory effects. This mechanism results in several anti-inflammatory actions, which have been documented in various studies:

Inhibition of Pro-Inflammatory Cytokines: Losartan has been shown to reduce the expression of inflammatory cytokines, such as interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α). This was observed in a rat model of chemotherapy-induced neuropathic pain and in macrophage studies.
Modulation of Cellular Signaling: Studies have revealed that losartan can suppress inflammatory responses by inhibiting key signaling pathways like NF-κB and MAPK (mitogen-activated protein kinase) in immune cells. This suppression is partly responsible for its anti-arthritic effects observed in animal models.
Attenuation of Fibrosis: In addition to its anti-inflammatory effects, losartan has well-documented anti-fibrotic properties by inhibiting the transforming growth factor-beta (TGF-β) pathway. This is particularly relevant in conditions affecting the kidneys and heart, where chronic inflammation and fibrosis lead to organ damage.

Potential Adverse Effects Mistaken for Inflammation

While losartan is generally anti-inflammatory, certain side effects can be mistaken for inflammatory responses. It is critical for patients to differentiate between these specific reactions and generalized inflammation.

Angioedema: This rare but serious allergic reaction causes swelling of the face, lips, tongue, or throat and requires immediate medical attention. Unlike the cough commonly associated with ACE inhibitors, angioedema with ARBs like losartan is less frequent but remains a risk.
Muscle and Joint Aches: Some individuals report muscle or joint aches (myalgia or arthralgia) while on losartan. The exact mechanism isn't fully understood, but it's believed to be related to the drug's metabolic interactions and not a widespread inflammatory process.
Edema: Swelling due to fluid retention is a possible side effect, which can sometimes be misinterpreted as inflammation. This is a distinct process, related to the drug's effect on fluid and electrolyte balance.

Losartan vs. ACE Inhibitors: A Comparison of Potential Inflammatory Reactions

Losartan belongs to the class of ARBs, which are often used as an alternative for patients who experience side effects from ACE inhibitors like lisinopril. The differences in how these two classes affect inflammatory-like reactions are noteworthy.


Feature	Losartan (ARB)	Lisinopril (ACE Inhibitor)
Mechanism	Blocks angiotensin II from binding to AT1 receptors.	Prevents the conversion of angiotensin I to angiotensin II.
Bradykinin	Does not affect bradykinin metabolism.	Inhibits the breakdown of bradykinin, leading to its accumulation.
Cough	Low incidence of persistent, dry cough.	Higher incidence of dry, irritating cough.
Angioedema	Lower incidence of angioedema compared to ACE inhibitors.	Known risk of angioedema due to bradykinin accumulation.
Anti-Inflammatory	Direct anti-inflammatory and anti-fibrotic effects.	Primarily through indirect effects on the renin-angiotensin system.

Nuances and Individual Responses

While preclinical and animal studies consistently show anti-inflammatory effects, human responses can vary. A notable clinical trial involving older HIV patients found that losartan did not significantly improve blood measures of inflammation (such as IL-6) or T-cell immune recovery, beyond the benefits of lowering blood pressure. This suggests that losartan's anti-inflammatory impact may not be clinically meaningful in all patient populations or for all types of inflammatory markers. Furthermore, for certain individuals, drug interactions or pre-existing conditions like kidney problems could influence the overall effect or risk of adverse events. For example, combining losartan with NSAIDs can increase the risk of acute kidney injury.

Conclusion

In conclusion, the premise that losartan causes widespread inflammation is largely inaccurate. Losartan, as an angiotensin II receptor blocker, is known for its beneficial anti-inflammatory and anti-fibrotic properties by targeting key components of the renin-angiotensin system. While it can lead to specific adverse reactions, such as allergic-type swelling (angioedema) or muscle aches, these are not indicative of a generalized inflammatory effect caused by the drug's primary action. Patient concerns related to inflammatory-like symptoms should be discussed with a healthcare provider to differentiate between true inflammatory processes and other drug side effects. Overall, losartan is a valuable medication that provides cardiovascular protection and, in many contexts, helps to modulate and reduce inflammatory signaling within the body.

What are the main takeaways regarding losartan and inflammation?

Anti-inflammatory Mechanism: Losartan's primary function as an angiotensin II receptor blocker (ARB) helps reduce inflammation by blocking the pro-inflammatory effects of angiotensin II.
Adverse Reactions vs. Inflammation: Symptoms like allergic reactions (angioedema), muscle pain, or swelling are specific adverse effects and not a sign that losartan causes systemic inflammation.
Pathways Inhibited: Losartan has been shown to reduce inflammatory cytokines (like TNF-α and IL-1β) and inhibit signaling pathways (like NF-κB and MAPK) in various studies.
Variable Clinical Effects: While often anti-inflammatory, studies suggest the clinical impact on systemic inflammatory markers can vary and may not be significant in all patient groups, such as those with HIV.
Different from ACE Inhibitors: Losartan poses a lower risk of cough and angioedema compared to ACE inhibitors like lisinopril, which are more associated with bradykinin accumulation.

Frequently Asked Questions

Yes, muscle pain or cramps and joint aches are reported side effects of losartan. The exact cause is not fully understood, but it is not typically due to a systemic inflammatory response. If you experience persistent pain, consult your doctor.

Angioedema, a rare but serious side effect of losartan, is a severe allergic-type reaction that causes swelling. While it has inflammatory components, it is not a sign that the medication is causing generalized inflammation throughout the body. It is an adverse reaction that requires immediate medical attention.

Losartan primarily lowers blood pressure by relaxing blood vessels. The anti-inflammatory effect is a secondary benefit related to its mechanism of blocking angiotensin II, a hormone involved in both blood pressure regulation and inflammatory pathways.

No, long-term use of losartan is not known to cause chronic inflammation. In fact, it is often prescribed long-term to protect organs from damage associated with chronic high blood pressure and fibrosis. Your doctor will monitor your overall health with regular blood tests.

Other angiotensin receptor blockers (ARBs), such as valsartan and candesartan, work similarly to losartan and also exhibit anti-inflammatory effects. Other drug classes might have different mechanisms for reducing inflammation.

ACE inhibitors can cause a buildup of bradykinin, which is responsible for the common side effects of a dry cough and a higher risk of angioedema. Losartan does not affect bradykinin, leading to a much lower incidence of these side effects.

Some animal studies suggest losartan has anti-arthritic effects by suppressing inflammatory pathways and preventing joint destruction in rat models of arthritis. However, it is not approved for this use in humans, and patients with arthritis should follow their doctor's treatment plan for that condition.