Balancing lung health and liver safety in pulmonary hypertension treatment

Liver Health Alert: Are Your PAH Meds Putting You at Risk?

Theo Raines monogram
Theo Raines in Health & Wellness October 2026 • 4 min read.

"A deep dive into the safety of pulmonary hypertension treatments and what you need to know to protect your liver."


Pulmonary hypertension (PAH) is a serious condition and managing it often involves a combination of medications. While these drugs can significantly improve your quality of life, it's essential to be aware of their potential side effects. Some medications used to treat PAH can, in rare cases, affect the liver, which is why ongoing research and monitoring are so important.

A recent analysis of the AMBITION trial sheds light on the liver safety of ambrisentan (an endothelin receptor antagonist, or ERA) when used alone or in combination with tadalafil (a phosphodiesterase-5 inhibitor). This study provides valuable insights for both patients and healthcare providers, helping to inform treatment decisions and monitoring strategies.

This article breaks down the key findings of the AMBITION trial analysis, explaining what they mean for your liver health if you're taking these medications. We'll cover the potential risks, how they're monitored, and what to discuss with your doctor to ensure your treatment plan is as safe and effective as possible.

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The Burden of Portopulmonary Hypertension

Portopulmonary hypertension (POPH) affects 5% to 6% of patients with advanced liver disease and accounts for 5% to 15% of pulmonary arterial hypertension (PAH) cases. Compared with idiopathic PAH, POPH is associated with significantly worse survival. PAH is a rare, progressive disease in which the small arteries carrying blood from the heart to the lungs become narrowed, stiffened, and thickened.

Management Requires Careful Coordination

Management of pulmonary hypertension in chronic liver disease generally combines screening, confirmation of the diagnosis, pulmonary vasodilator therapy, and consideration of liver transplantation based on disease severity and treatment response. Reviews describe PAH therapy as requiring unique treatment considerations when comorbid liver disease is present. However, optimal management remains difficult to define because clinical-trial evidence for PAH therapies is limited and the role of liver transplantation remains uncertain. Hemodynamic assessment can help distinguish isolated postcapillary pulmonary hypertension from co-existing precapillary pulmonary hypertension with pulmonary vasculopathy, but the assessment has limitations.

An Evolving Field

The history of PAH care reflects a gradually developing understanding of how pulmonary vascular disease and liver disease can intersect. Foundational milestones likely include improvements in disease recognition, diagnostic evaluation, and targeted therapy, although the available source material does not document specific historical discoveries or dates. The field continues to evolve as researchers refine diagnostic and treatment strategies.

Understanding the AMBITION Trial and Liver Safety

Balancing lung health and liver safety in pulmonary hypertension treatment

The AMBITION trial was a significant study in the field of pulmonary hypertension, designed to evaluate the effectiveness of initial combination therapy with ambrisentan and tadalafil. Now, a new analysis has focused on the liver safety aspect of these treatments. Researchers looked at data from 596 patients with PAH who were randomly assigned to receive ambrisentan or tadalafil as a single therapy, or a combination of both. They specifically looked for elevations in liver enzymes (ALT/AST) and bilirubin, which can indicate liver problems.

The study found that elevations in ALT/AST levels (more than three times the upper limit of normal) occurred in a small percentage of patients:

  • 3.4% to 3.7% of patients during the study period, with an annualized incidence of 2.1% to 2.93%.
  • The majority of these patients had elevations that were only mildly elevated (between 3 and 5 times the upper limit of normal).
  • A very small number of patients (0.5%) had ALT/AST elevations combined with elevated bilirubin, a condition that raises more concern for potential drug-induced liver injury.
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Research Continues to Refine PAH Care

Recent reviews continue to examine how PAH should be evaluated and managed, particularly when pulmonary vascular disease occurs alongside liver disease. Current literature appears to emphasize diagnostic clarification, treatment selection, and the unresolved evidence base surrounding liver transplantation. Because no source material was provided for this subsection, these observations should be treated as a general overview rather than a summary of specific new findings.

Important Gaps and Diagnostic Limits

Portopulmonary hypertension is one of the major pulmonary complications associated with portal hypertension, but diagnosis and treatment remain challenging. Transthoracic echocardiography (TTE) has limitations in diagnosing portopulmonary hypertension, and not all patients with portal hypertension are screened; current guidelines recommend TTE screening when symptoms are present or during evaluation for liver transplantation. Targeted pulmonary hypertension medications are supported by years of research and clinical trials, but these therapies must be considered within the broader complexity of liver-associated disease.

Comparing Treatment Contexts

PAH associated with liver disease cannot necessarily be approached in exactly the same way as idiopathic PAH because clinicians must account for portal hypertension, liver function, and possible transplant evaluation. Comparisons between treatment strategies should therefore consider both pulmonary hemodynamics and the patient's hepatic condition. The available source material does not provide comparative trial results for specific medications or patient groups.

Importantly, the researchers concluded that ambrisentan, whether used alone or with tadalafil, was not associated with drug-induced liver injury in this study. The few patients who did experience liver enzyme elevations often had other probable causes, such as cardiogenic shock, liver metastases, or lymphoma.

What This Means for You and Your Treatment

The AMBITION trial analysis offers reassurance regarding the liver safety of ambrisentan and tadalafil. However, it's crucial to remember that all medications carry potential risks, and individual responses can vary. Regular monitoring of liver function remains an important part of managing PAH.

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Balancing Pulmonary and Liver Health

The relationship between PAH and liver disease calls for coordinated assessment rather than a narrow focus on pulmonary pressure alone. A practical synthesis is to confirm the diagnosis, evaluate disease severity, consider targeted therapy, and address whether liver transplantation is appropriate. The available source material does not include direct expert commentary or a specific consensus recommendation beyond these broad themes.

New Targets and Therapies

Future PAH research is investigating new molecules, pathways, and formulations for treatment. Reviews report that preclinical and clinical research has identified several novel therapeutic targets, particularly within the pathophysiological pathways of WHO Group I PAH. A 2025 review describes PAH as a complex, progressive disease marked by elevated pulmonary vascular resistance and right heart failure, while a 2026 overview highlights advances in understanding PAH pathobiology, epidemiology, diagnosis, and treatment.

PAH as a Multisystem Challenge

Effective PAH care faces patient-related and system-level obstacles that can hinder diagnosis, management, and treatment. PAH is increasingly recognized as a multi-organ disease involving the systemic circulation, kidneys, skeletal muscles, and central nervous system, among other systems. These broader effects make coordinated, accessible care important, especially when liver abnormalities are also present.

Treatment Can Affect Liver Outcomes

Liver injury patterns have been associated with adverse outcomes in patients with PAH and chronic thromboembolic pulmonary hypertension (CTEPH). In the clinical trials reviewed, randomization to active pulmonary hypertension treatment had beneficial effects on liver health compared with placebo. For portopulmonary hypertension, targeted pulmonary vasodilator therapy and liver transplantation are central management considerations, with treatment expected to influence hemodynamic and clinical outcomes.

Here's what you should discuss with your doctor:

<ul> <li>Your individual risk factors for liver problems.</li> <li>The potential side effects of all your PAH medications.</li> <li>The schedule for monitoring your liver function.</li> <li>Any new symptoms you experience that could indicate liver issues (such as jaundice, abdominal pain, or fatigue).</li> </ul>

Ambrisentan registry rates against the assumed background

  • 0.02 events per patient-yearThe registry reported an incidence of aminotransferase events above 3× ULN of 0.02 per patient-year, with a 95% confidence interval from 0.015 to 0.027.[1]Caveat: 95% confidence interval 0.015 to 0.027

What the liver-safety comparisons can establish

The registry comparison places ambrisentan-related enzyme elevations alongside an assumed background rate, rather than showing that such elevations never occur. Its observational design and physician-collected monitoring mean the result describes routine records, not a controlled causal test.[1] [2]

A proposed explanation for ambrisentan's lower rate is its metabolism independent of cytochrome P450, but the source presents this as a possibility, not an established mechanism.[3]

How ambrisentan compares with other endothelin-receptor antagonists

A meta-analysis found abnormal liver function more often across the ERA group than with placebo; its drug-specific comparisons differed, with a higher risk for bosentan but no increased risk detected for ambrisentan or macitentan.[4] [5]

Earlier clinical-trial reports give liver-enzyme elevation ranges for bosentan and sitaxsentan, but those figures alone do not establish a lower ambrisentan incidence.[3]

The evidence base for ERAs other than bosentan is too limited to support firm conclusions about each drug's individual risk. A separate comparison of discontinuation-level abnormalities between ambrisentan and other ERAs had not been made in the cited source.[3] [6]

What remains uncertain about liver findings

  • Because information on coexisting conditions and other medications was limited to what trial case-report forms captured, how much these factors contributed to elevations remains uncertain.[2] [7]
  • The post-hoc analysis evaluated patients with normal baseline hepatic function, but its design leaves open whether selection affected the results; the cited analysis also does not settle individual risk across the remaining ERA drugs.[2] [6]

Sources

  1. Ambrisentan use for pulmonary arterial hypertension in a post-authorization drug registry: The VOLibris Tracking Study. (pubmed.ncbi.nlm.nih.gov)
  2. Hepatic safety of ambrisentan alone and in combination with tadalafil: a post-hoc analysis of the AMBITION trial (pmc.ncbi.nlm.nih.gov)
  3. Ambrisentan for the treatment of pulmonary arterial hypertension (pmc.ncbi.nlm.nih.gov)
  4. Clinical Adverse Effects of Endothelin Receptor Antagonists: Insights From the Meta-Analysis of 4894 Patients From 24 Randomized Double-Blind Placebo-Controlled Clinical Trials. (pubmed.ncbi.nlm.nih.gov)
  5. Clinical Adverse Effects of Endothelin Receptor Antagonists: Insights From the Meta‐Analysis of 4894 Patients From 24 Randomized Double‐Blind Placebo‐Controlled Clinical Trials (pmc.ncbi.nlm.nih.gov)
  6. [Hepatotoxicity in patients treated with endothelin receptor antagonists: systematic review and meta-analysis of randomized clinical trials]. (pubmed.ncbi.nlm.nih.gov)
  7. www.ema.europa.eu (www.ema.europa.eu)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

What was the primary focus of the AMBITION trial concerning pulmonary hypertension treatments?

The AMBITION trial focused on evaluating the effectiveness of initial combination therapy using ambrisentan and tadalafil for pulmonary hypertension. A specific analysis examined liver safety, monitoring patients for elevations in liver enzymes (ALT/AST) and bilirubin, which are indicators of potential liver issues. The trial's design involved randomly assigning patients with PAH to receive either ambrisentan alone, tadalafil alone, or a combination of both, allowing researchers to compare the liver safety profiles of these treatment approaches.

2

According to the AMBITION trial analysis, what were the rates of liver enzyme elevations observed in patients taking ambrisentan and tadalafil?

The analysis of the AMBITION trial indicated that elevations in ALT/AST levels (more than three times the upper limit of normal) occurred in 3.4% to 3.7% of patients during the study period, with an annualized incidence of 2.1% to 2.93%. Most of these patients experienced only mildly elevated liver enzyme levels. A very small percentage of patients (0.5%) had ALT/AST elevations combined with elevated bilirubin, raising concerns for potential drug-induced liver injury. However, the researchers concluded that ambrisentan, whether used alone or with tadalafil, was not associated with drug-induced liver injury in this study.

3

How should the findings from the AMBITION trial influence the management of pulmonary hypertension, particularly concerning liver health?

The AMBITION trial analysis suggests that ambrisentan and tadalafil do not pose a significant risk to the liver when used to treat pulmonary hypertension. However, regular monitoring of liver function is essential. This is because all medications carry potential risks and individual responses can vary. Regular monitoring can help detect any potential liver issues early, allowing for timely intervention and adjustments to the treatment plan.

4

How do ambrisentan and tadalafil work in the body to treat pulmonary hypertension, and why is this important for understanding their effects?

Endothelin receptor antagonists (ERAs) like ambrisentan, work by blocking the action of endothelin, a substance that causes blood vessels to narrow. By blocking endothelin, these drugs help to relax and widen the blood vessels in the lungs, reducing blood pressure and improving blood flow. Phosphodiesterase-5 inhibitors, such as tadalafil, work by increasing the levels of nitric oxide, another substance that helps relax blood vessels. These drugs are effective for pulmonary hypertension because they target different pathways involved in regulating blood vessel tone and pressure in the lungs. Combining these drugs can provide a synergistic effect, improving both symptoms and exercise capacity.

5

Beyond ambrisentan and tadalafil, what other pulmonary hypertension medications might impact liver health, and how should these be monitored?

While the AMBITION trial analysis focused on ambrisentan and tadalafil, other PAH medications also require consideration for liver safety. For example, bosentan is another ERA that has been associated with liver enzyme elevations. Sildenafil is another phosphodiesterase-5 inhibitor. Prostanoids (e.g., epoprostenol, treprostinil) and prostacyclin receptor agonists (e.g., selexipag) are also used to treat PAH. It's essential to discuss the potential liver-related risks of all medications with your healthcare provider and undergo regular monitoring, as recommended.

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