Medical Uses of Lysine
Antifibrinolytic Therapy (Lysine Analogues)
Lysine analogues—specifically tranexamic acid and ε-aminocaproic acid—are primarily used in medical practice to prevent and control bleeding by inhibiting fibrinolysis. These synthetic lysine derivatives competitively inhibit plasmin and plasminogen, preventing the breakdown of fibrin clots 1.
Tranexamic Acid Dosing
- Loading dose: 10-15 mg/kg IV followed by continuous infusion of 1-5 mg/kg/hour 1, 2
- Alternative regimen: 1 g IV bolus over 10 minutes, followed by 1 g infusion over 8 hours 3
- Plasma half-life: Approximately 120 minutes, requiring continuous infusion to maintain therapeutic levels of 10 μg/ml needed to inhibit fibrinolysis 1
ε-Aminocaproic Acid Dosing
- Loading dose: 150 mg/kg followed by continuous infusion of 15 mg/kg/hour 1
- Note: This agent has 10-fold weaker potency than tranexamic acid, necessitating higher doses 1
Clinical Applications of Lysine Analogues
Cardiac and thoracic aortic surgery: Lysine analogues (epsilon-aminocaproic acid 75-150 mg/kg bolus with 12.5-30 mg/kg/h infusion; tranexamic acid 2.5-100 mg/kg bolus with 0.25-4.0 mg/kg/h infusion) are commonly used to counteract fibrinolysis during cardiopulmonary bypass 1.
Major trauma with significant hemorrhage: Antifibrinolytic agents should be considered for bleeding trauma patients, though evidence specific to trauma is limited compared to elective surgery 1.
Fibroid-related bleeding: Tranexamic acid serves as a nonhormonal alternative to reduce bleeding symptoms in patients with fibroids 2.
Safety Considerations
- Thrombotic risk: Despite theoretical concerns, studies including over 8,000 patients demonstrated no increased risk of arterial or venous thrombotic events with lysine analogues 1
- Renal dysfunction: Lysine analogues are renally excreted and accumulate in renal failure; dosage reduction is required based on serum creatinine levels 1, 2, 4
- Contraindications: Active intravascular coagulation is an absolute contraindication 3
- Drug interactions: Use caution when combining tranexamic acid with oral contraceptives due to increased thrombotic risk 2
Nutritional/Supplemental Lysine
Carnitine Synthesis
L-lysine serves as a precursor for endogenous carnitine synthesis (along with methionine), which is required for transporting long-chain fatty acids into mitochondria for energy generation 1. One small randomized trial suggested potential mortality benefit in septic shock patients treated with IV L-carnitine within 24 hours of shock onset, though the trial was underpowered 1.
Viral Infection Claims (Herpes Simplex)
The evidence for L-lysine supplementation in preventing or treating herpes simplex virus infections is weak and inconsistent:
- Doses <1 g/day appear ineffective for prophylaxis or treatment of herpes simplex lesions 5
- Doses >3 g/day may improve subjective patient experience of the disease, but definitive evidence is lacking 5
- The proposed mechanism involves competitive antagonism with arginine, which some viruses require for replication 6, 7
- Cardiovascular and gallbladder disease patients should be cautioned about theoretical risks of lysine supplementation 5
Other Viral Infections
- In vitro studies suggest lysine may block SARS-CoV-2 and influenza A virus infection by potentially disturbing virus uncoating 6
- One case report suggested L-lysine accelerated resolution of pityriasis rosea (suspected HHV-6/7 association) 8
- However, lysine supplementation is NOT effective for feline herpesvirus 1 and may even worsen outcomes 9
Critical Caveat
Lowering arginine levels through lysine supplementation is potentially dangerous in cats (who cannot synthesize arginine), resulting in hyperammonemia that may be fatal 9. This highlights the importance of understanding species-specific amino acid metabolism before recommending supplementation.