Can Losartan (angiotensin II receptor antagonist) cause bradycardia?

From the Guidelines

Losartan is not typically associated with causing bradycardia as a direct effect, but it may contribute to bradycardia through indirect mechanisms, particularly in patients with pre-existing cardiac conditions or those taking other heart rate-slowing medications 1.

Mechanism and Risk Factors

Losartan, an angiotensin II receptor blocker (ARB), primarily works by blocking the vasoconstricting and aldosterone-secreting effects of angiotensin II, leading to blood pressure reduction. While its direct effect on heart rate is not typically significant, the blood pressure-lowering effect can trigger compensatory responses from the body, including changes in heart rate. Patients with pre-existing cardiac conduction disorders, those taking other medications that slow heart rate (like beta-blockers or certain calcium channel blockers), or elderly patients may be at higher risk for developing bradycardia while on losartan.

Clinical Considerations

If a patient experiences symptoms of bradycardia such as dizziness, fatigue, weakness, or syncope while taking losartan, they should seek medical attention promptly. Healthcare providers may need to adjust the dosage or consider alternative medications depending on the severity of symptoms and the patient's overall clinical picture. The LIFE study, which compared losartan with a β-adrenergic receptor blocker in patients with essential hypertension and electrocardiographically determined LV hypertrophy, found similar blood pressure reductions but a significant reduction in major vascular events in the losartan group 1. However, this study does not directly address the incidence of bradycardia.

Evidence and Recommendations

The most recent and highest quality evidence does not specifically address losartan's effect on heart rate or the incidence of bradycardia as a primary outcome. However, given the potential for indirect effects on heart rate, particularly in vulnerable populations, healthcare providers should monitor patients on losartan for signs of bradycardia, especially if they are also taking other medications that can slow heart rate 1. This cautious approach prioritizes patient safety and allows for timely intervention if bradycardia or other adverse effects occur.

From the FDA Drug Label

There was essentially no change in average heart rate in losartan-treated patients in controlled trials. The most likely manifestation of overdosage would be hypotension and tachycardia; bradycardia could occur from parasympathetic (vagal) stimulation.

Losartan and Bradycardia:

• Losartan does not typically cause bradycardia, as there was essentially no change in average heart rate in patients taking the medication in controlled trials 2.
• However, in cases of overdosage, bradycardia could occur from parasympathetic (vagal) stimulation 2. It is essential to note that this is in the context of an overdose, not a typical dosage.

From the Research

Losartan and Bradycardia

• Losartan is an angiotensin II receptor antagonist used to treat hypertension and heart failure 3.
• The effect of losartan on heart rate, including the potential to cause bradycardia, has been studied in various clinical trials and experiments.

Evidence from Studies

• A study published in 2005 found that losartan accentuated the orthostatic hypotensive response in anesthetized rats and caused a significant bradycardia [-8+/-3% after losartan vs -3+/-3% control tilt] 4.
• Another study from 1999 investigated the effect of losartan on heart rate and blood pressure variability during a tilt test and trinitroglycerine vasodilation, but did not report a significant decrease in heart rate 5.
• The study from 2000 reviewed the use of losartan in elderly patients with hypertension and did not mention bradycardia as a common side effect 6.
• Other studies have focused on the renal effects of losartan and its use in patients with non-diabetic nephropathy, without reporting any significant effects on heart rate 7.

Key Findings

• Losartan may cause bradycardia in certain situations, such as orthostatic stress, as shown in the study on anesthetized rats 4.
• However, the evidence from human studies is limited, and more research is needed to fully understand the effects of losartan on heart rate and the potential for bradycardia 4, 5.