Indications
L-Lysine is an essential amino acid, a protein building block that the body cannot make and must get from food. As a supplement, usually in syrups or tablets combined with vitamins, it is used to support appetite, growth and general nutrition in children and adults with poor diet or recovering from illness. It is also sometimes used to help reduce the frequency of cold sores (herpes simplex), although evidence for this is mixed. In some gels it is combined with other ingredients for skin or gum care.
How It Works
Lysine is needed to build body proteins, muscle, enzymes, hormones and antibodies, to make collagen for skin, bones and connective tissue, and to help absorb calcium from the gut. It may compete with arginine, another amino acid that the cold sore virus needs to multiply.
Dosage and Administration
Use as directed on the label or by your doctor. Vitamin syrups and tablets containing lysine are usually taken once or twice a day with or after food, with the amount depending on age. For cold sore prevention, adults commonly take about 1 g a day; do not exceed the label dose. Topical gels are applied as directed on the pack.
Interactions
Lysine may increase calcium absorption; take care with high-dose calcium supplements. It may interact with aminoglycoside antibiotics such as Gentamicin, possibly increasing kidney risk. If you take other medicines regularly, ask a pharmacist before using high-dose lysine.
Contraindications
Do not use if you are allergic to any ingredient. People with rare inherited disorders of lysine metabolism (such as lysinuric protein intolerance) should not use lysine supplements. People with kidney disease should use high doses only on medical advice.
Side Effects
At usual amounts it is well tolerated. High doses may cause stomach pain, nausea or diarrhoea. Rarely, very high long-term doses have been linked to kidney problems.
Get urgent medical help if you develop swelling of the face, lips or throat, difficulty breathing, a widespread rash, or reduced urine with swelling of the legs.
Pregnancy and Lactation
Lysine from food is safe in pregnancy and breastfeeding. Supplement doses above normal dietary amounts have not been well studied; ask your doctor before using them.
Precautions and Warnings
Supplements do not replace a balanced diet. If a child has poor appetite or poor growth for a long time, see a doctor to look for underlying causes. Check the label for sugar content if you have diabetes, and for other vitamins in combination products to avoid doubling up.
Overdose
Taking too much may cause stomach upset and diarrhoea. If a large amount is swallowed, especially by a child, contact a doctor.
Therapeutic Class
Amino acid nutritional supplement.
Storage
Store below 30°C in a dry place, away from light and out of the reach of children. Use syrups within the time stated on the label after opening.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.