Amantadine and Ammonia Levels
No increase in ammonia levels has been observed among persons taking amantadine, even in those with liver disease. 1
Amantadine and Liver Function
- Amantadine has not been associated with increased adverse reactions in patients with liver disease 1
- Only rare instances of reversible elevation of liver enzymes have been reported among patients receiving amantadine, though a specific causal relationship between the drug and such changes has not been established 1
- Unlike some medications that require dosage adjustments for hepatic impairment, amantadine does not require dose modification based on liver function 1
Pharmacokinetics of Amantadine
- Approximately 90% of amantadine is excreted unchanged in the urine through glomerular filtration and tubular secretion 1
- Amantadine's metabolism is primarily renal rather than hepatic, which explains why liver function has minimal impact on its clearance 2, 3
- Dosage adjustments are required for renal impairment but not for hepatic dysfunction 1
Clinical Considerations
- For patients with renal insufficiency, amantadine dosage should be reduced as the drug can accumulate due to decreased renal clearance 2, 3
- Hemodialysis contributes minimally to amantadine clearance, removing less than 5% of the dose during a 4-hour session 2
- Patients with seizure disorders should be monitored closely when taking amantadine due to potential increased seizure activity 1
Hyperammonemia Considerations
- Hyperammonemia is primarily associated with liver disorders and can lead to hepatic encephalopathy 4, 5
- Elevated ammonia levels can cause alterations in astrocyte morphology, cerebral energy metabolism, and neurotransmission 6
- While certain medications can exacerbate hyperammonemia in susceptible individuals, amantadine has not been documented to have this effect 5, 1
Monitoring Recommendations
- Standard monitoring of liver function is not specifically required when using amantadine, unlike some other medications that have hepatic metabolism 1
- For patients with pre-existing liver disease who are starting amantadine, routine monitoring of liver enzymes may be prudent, though not specifically mandated by guidelines 1
- If a patient develops signs of hepatic dysfunction while on amantadine, consider other causes as amantadine is not typically associated with liver injury 1