From the Guidelines
Hyperammonemia is primarily caused by conditions that impair the body's ability to process ammonia, including liver dysfunction and genetic disorders, and its treatment should focus on lowering ammonia levels through multiple approaches, as recommended in the most recent guidelines 1. The main causes of hyperammonemia include:
- Liver cirrhosis
- Acute liver failure
- Hepatitis
- Urea cycle disorders
- Certain medications, such as valproic acid
- Metabolic conditions Treatment of hyperammonemia involves:
- First-line medications: lactulose (20-30g orally, 3-4 times daily) and rifaximin (550mg, twice daily) to reduce ammonia production and enhance its removal
- Protein restriction (0.5-0.8g/kg/day) to reduce ammonia production
- Hemodialysis or continuous renal replacement therapy in critical situations
- Specific treatments for genetic urea cycle disorders, including sodium phenylbutyrate, sodium benzoate, or arginine supplementation, as outlined in recent consensus guidelines 1
- Intravenous L-ornithine L-aspartate for severe cases, as supported by recent studies 1 It is essential to treat the underlying cause of hyperammonemia for long-term management, and prompt treatment is crucial to prevent neurological damage, brain edema, and potentially death, as highlighted in recent clinical practice guidelines 1.
From the FDA Drug Label
Arginine Administration Intravenous arginine is an essential component of therapy for patients with carbamyl phosphate synthetase (CPS), ornithine transcarbamylase (OTC), argininosuccinate synthetase (ASS), or argininosuccinate lyase (ASL) deficiency Hyperammonemia due to urea cycle disorders should be managed in coordination with medical personnel experienced in metabolic disorders.
The causes of high ammonia levels include:
- Urea cycle disorders such as carbamyl phosphate synthetase (CPS), ornithine transcarbamylase (OTC), argininosuccinate synthetase (ASS), or argininosuccinate lyase (ASL) deficiency 2 Hyperammonemia can be treated with:
- Intravenous arginine for patients with CPS, OTC, ASS, or ASL deficiency
- Sodium Phenylacetate and Sodium Benzoate Injection, 10%/10% to reduce ammonia levels
- Hemodialysis to eliminate ammonia and ammonia conjugates
- Caloric supplementation and restriction of dietary protein to manage hyperammonemia 2
From the Research
Causes of Hyperammonemia
- Hyperammonemia develops if the urea cycle cannot control the ammonia load, which occurs when the load is excessive, portal blood from the intestines bypasses the liver, and/or the urea cycle functions poorly 3.
- Liver damage is the most common cause of hyperammonemia, but other causes in adults include unsuspected inherited defects of the urea cycle and fatty acid oxidation presenting with catastrophic illness in previously normal individuals 3.
- Hepatic encephalopathy (HE) is a serious neuropsychiatric complication that is seen in patients with liver failure, and ammonia is considered the main culprit behind primary and secondary symptoms 4.
- Hyperammonemia can also be caused by an inherited or acquired impairment in hepatic detoxification, leading to potentially life-threatening neuropsychiatric symptoms 5.
Treatment of Hyperammonemia
- Most treatments of hyperammonemia target the organs and metabolic processes involved in ammonia detoxification, including lactulose and rifaximin, which have a proven role as measures to use for secondary prophylaxis 4.
- The use of molecular adsorbent recirculating system in patients with severe HE has been proven to be efficacious, but through mechanisms that appear to be independent of ammonia 4.
- Inhibition of receptor-interacting serine/threonine-protein kinase 1 (RIPK1) and its upstream inducer Toll-like receptor 4 (TLR4) may protect against liver injury and further hyperammonemia 6.
- Recent advances in treating hyperammonemia include using synergistic combination treatments, broadening the indication of orphan drugs, and developing novel approaches to regenerate functional liver tissue 5.
Clinical Impact of Hyperammonemia
- Elevated serum ammonia contributes to neurotoxicity, sarcopenia, and immune dysfunction in cirrhosis 7.
- Serum ammonia levels have prognostic value and have been implicated in hepatotoxicity and immune dysfunction 7.
- Hyperammonemia induces liver fibrogenesis and RIPK1-mediated cell death, which is associated with urea cycle dysfunction 6.