L-Lysine Hydrochloride

A. Nutritional Uses

• Treatment and prevention of lysine deficiency in individuals with inadequate dietary intake or increased metabolic demand (e.g., athletes, malnourished individuals, or patients with restrictive diets).
• Amino acid supplementation in Total Parenteral Nutrition (TPN) for patients unable to maintain sufficient oral or enteral intake.

B. Supportive Medical Uses (Clinically Accepted Off-label)

• Adjunctive therapy for herpes simplex virus (HSV) infections, particularly recurrent herpes labialis and herpes genitalis, to help reduce outbreak frequency and severity.
• Bone health and calcium absorption support in patients with osteopenia or osteoporosis, as lysine aids in calcium utilization and collagen synthesis.
• Supportive role during periods of high stress or tissue repair, such as post-surgery or injury, where amino acid demands are elevated.

Adults

• Oral (nutritional supplementation): 500 mg to 1,000 mg orally 1 to 3 times daily, based on deficiency severity.
• Oral (herpes simplex, off-label): 1,000 mg orally 1 to 3 times daily during outbreaks; maintenance dose: 500 mg once or twice daily to prevent recurrence.
• Parenteral (as part of TPN): Included in amino acid mixtures; dosing individualized per patient’s protein and nitrogen needs.

Pediatrics

• Dosage based on weight and clinical condition; commonly 100 mg/kg/day orally in divided doses.
• For parenteral use, standard pediatric TPN solutions contain lysine in balanced amino acid concentrations.

Elderly

• Same as adult dosing. Monitor renal function and adjust dose if necessary, particularly in parenteral administration.

Renal Impairment

• Use with caution. Dosage adjustment may be required, especially in moderate to severe renal impairment due to reduced amino acid clearance. Close monitoring is advised.

Route of Administration

• Oral: Tablets, capsules, or powder
• Intravenous: Only as a component of amino acid mixtures in TPN

Duration of Use

• Varies by indication. May be short-term (nutritional correction) or long-term (herpes prevention or chronic support).

L-Lysine is an essential α-amino acid necessary for protein synthesis, collagen formation, and calcium absorption. It plays a critical role in the production of enzymes, hormones, and antibodies. In herpes simplex infections, lysine acts by inhibiting the absorption and utilization of arginine, another amino acid essential for HSV replication. By reducing arginine availability, lysine interferes with viral protein synthesis, thereby reducing the severity and frequency of outbreaks. Additionally, lysine supports tissue repair and immune function, making it beneficial in stress-related catabolic states.

• Absorption: Rapid and efficient absorption from the gastrointestinal tract after oral administration.
• Distribution: Widely distributed throughout body tissues; high concentrations found in muscle and connective tissue.
• Metabolism: Primarily metabolized in the liver via transamination pathways; minimal hepatic enzyme involvement.
• Excretion: Mainly eliminated by the kidneys through urinary excretion, both as unchanged lysine and metabolites.
• Bioavailability: Approximately 90% with oral formulations.
• Half-life: Typically 3 to 5 hours, may vary with formulation and renal function.
• Elimination Route: Renal excretion via urine.

• Pregnancy:
  L-Lysine is categorized as Generally Recognized As Safe (GRAS) when used in dietary amounts. No teratogenic effects have been reported. High doses should be avoided unless medically indicated.
• Lactation:
  Excreted into breast milk in small amounts. Considered safe when taken at standard dietary levels. High-dose supplementation should be used with caution due to limited safety data in lactating mothers.
• Note: Always consult a healthcare provider before initiating high-dose lysine supplementation during pregnancy or breastfeeding.

• Primary Class: Amino Acid Supplement
• Subclass: Essential Amino Acid
• Pharmacologic Role: Nutritional support, antiviral adjunct, metabolic enhancer

• Hypersensitivity to L-lysine or any component of the formulation
• Severe hepatic failure (due to potential nitrogen overload)
• Advanced renal impairment without dialysis support (risk of amino acid accumulation)
• Known hyperlysinemia (rare metabolic disorder)

• Renal Impairment: Use cautiously; monitor renal function during prolonged or high-dose use, especially with TPN.
• Hepatic Impairment: Caution in severe liver dysfunction due to risk of nitrogen overload.
• High-dose Use: Long-term use of high doses may lead to gastrointestinal upset or metabolic imbalances.
• Herpes Treatment: Lysine is not a substitute for antiviral medications in severe or systemic infections.
• Electrolyte Monitoring: Monitor calcium and nitrogen balance during parenteral therapy.

Common (by system):

• Gastrointestinal: Nausea, diarrhea, abdominal cramping, bloating
• Neurological: Headache, dizziness (rare)
• Dermatological: Mild rash or itching (infrequent)

Serious (rare):

• Nephrotoxicity in patients with preexisting renal dysfunction
• Hypercalcemia when combined with excessive calcium supplementation
• Metabolic disturbances in prolonged high-dose or TPN use

Timing and Dose Dependence:

• Most side effects are dose-related and occur with intakes above 3 g/day.
• GI symptoms usually resolve with dose reduction.

• Arginine: Competitive antagonism; lysine may reduce arginine activity, affecting viral suppression or metabolic balance.
• Calcium Supplements: Lysine enhances calcium absorption; monitor serum calcium in patients receiving both.
• Nephrotoxic Drugs (e.g., aminoglycosides): Additive nephrotoxicity risk when used concurrently in high doses or with TPN.
• CYP450 Enzymes: L-lysine does not significantly interact with CYP450 enzymes, minimizing hepatic drug interaction potential.

Drug-Food Interactions:
No significant interactions. High-protein meals may increase overall amino acid load but are not clinically significant unless excessive.

• TPN Guidelines: Recent nutrition protocols emphasize the essential role of lysine in balanced amino acid formulations.
• HSV Management: Continued investigation into lysine’s adjunctive benefit in recurrent HSV; still considered supportive, not primary therapy.
• No new regulatory warnings or major dosage changes reported by FDA, EMA, or WHO as of current data.

Oral Formulations (Tablets, Capsules, Powder):

• Store at 20°C to 25°C (68°F to 77°F)
• Protect from moisture and direct sunlight
• Keep in a tightly closed container

Parenteral Formulations (in TPN):

• Store unopened vials or admixtures at 2°C to 8°C (36°F to 46°F)
• Do not freeze
• Use promptly after reconstitution or admixture
• Protect from light if stored for prolonged periods