Can L-carnitine (levocarnitine) injections affect liver enzymes?

Effect of L-Carnitine Injection on Liver Enzymes

L-carnitine injections can significantly reduce liver enzymes including ALT, AST, and GGT, particularly in patients with liver diseases, when administered at higher doses (≥2000 mg/day) for longer durations (>12 weeks). 1, 2

Mechanism and Effects on Liver Enzymes

L-carnitine plays a crucial role in fatty acid metabolism by facilitating the transport of long-chain fatty acids into mitochondria for β-oxidation. This process is particularly important for liver function and may explain its effects on liver enzymes:

• Reduction in liver enzymes: Meta-analyses of randomized controlled trials show that L-carnitine supplementation significantly decreases:

  • ALT by approximately 8.65-10.73 IU/L
  • AST by approximately 7.15-8.52 IU/L
  • GGT by approximately 7.40-8.80 IU/L 1, 2

• Dose-dependent effects: The hepatoprotective effects are more pronounced with:

  • Higher doses (≥2000 mg/day)
  • Longer treatment duration (>12 weeks)
  • In patients with pre-existing liver diseases 1

Clinical Considerations

When monitoring patients receiving L-carnitine injections:

• Liver function assessment: Investigation of suspected L-carnitine deficiency should include liver function tests (AST, ALT) along with triglycerides, glucose, lactate, ammonium, and urine ketones 3

• Patient populations most affected:

  • The effect on liver enzymes is most significant in patients with liver diseases
  • Effects are less pronounced or not significant in normal weight and healthy subjects 2
  • Patients on prolonged parenteral nutrition (PN) or continuous renal replacement therapy may benefit from L-carnitine supplementation (0.5-1 g/day) 3

• Potential hepatoprotective mechanisms:

  • Reduction in oxidative stress
  • Improvement in mitochondrial function
  • Anti-inflammatory properties 3
  • L-carnitine has been shown to reduce inflammatory markers like CRP and TNF-α in various patient populations 3

Cautions and Side Effects

• Dosing considerations: Pharmacologic supplementation is typically 50-100 mg/kg/day, with adults often receiving up to 3 g/day 3

• Potential side effects at doses ≥3 g/day:

  • Gastrointestinal symptoms (nausea, vomiting, abdominal cramps, diarrhea)
  • "Fishy" body odor due to trimethylamine metabolites
  • Rare side effects include muscle weakness in uremic patients and seizures in those with seizure disorders 3

Clinical Applications

• In patients with non-alcoholic fatty liver disease (NAFLD), L-carnitine (1g twice daily for 24 weeks) has shown effectiveness in improving liver function, reducing inflammatory markers, and improving histological manifestations 3

• In patients with hepatic encephalopathy, L-carnitine administration may help lower blood ammonia levels, reduce muscle loss, and increase physical activity 4, 5

• For patients on home parenteral nutrition with abnormal liver tests, the evidence for L-carnitine's effectiveness in reversing steatosis is mixed 6

While L-carnitine injections can affect liver enzymes, the clinical decision to use them should be based on the patient's specific condition, with particular consideration for those with liver diseases who may derive the greatest benefit.