Failure of lysine treatment in recurrent herpes simplex labialis

Comprehensive Safety Assessment of l-Lysine Supplementation from Clinical Studies: A Systematic Review

BACKGROUND

Despite the widespread use of l-lysine in dietary supplements, the safety information pertinent to excessive l-lysine ingestion is limited and, to the best of our knowledge, there is no published systematic review of safety.

OBJECTIVE

The objective of this study was to assess the clinical safety of l-lysine supplementation of a regular diet.

METHODS

We searched PubMed, Cochrane Library, Ichushi Web, and EBSCOhost using the relevant keywords, "l-lysine" and "clinical trial." To investigate all adverse events observed during intervention trials, we included all intervention studies with orally ingested l-lysine without restricting background factors, environment, study designs, and sample sizes.

RESULTS

We identified 71 articles, which included 3357 study subjects. The l-lysine doses ranged from 16.8 to 17.5 g/d, and the dosing period ranged from 1 to 1095 d. The observed adverse events were mainly subjective gastrointestinal tract symptoms; however, the risk analysis for incidence of gastrointestinal symptoms was not statistically significant (risk ratio of 1.02).

CONCLUSION

The provisional no-observed-adverse-effect level in healthy human subjects was based on gastrointestinal symptoms and identified at 6.0 g/d. The review protocol was registered at umin.ac.jp as UMIN000028914 before the beginning of the study.

Safety assessment of L-lysine oral intake: a systematic review

Currently, the use of amino acids in supplements and functional foods is increasing globally. However, there are no guidelines for the upper limit of ingestion for the safe use of these amino acids. Safety evaluation of chemical substances is generally performed through non-clinical and clinical studies. However, amino acids that have these safety data are limited. Therefore, we used a systematic review approach for evaluating the safety of amino acids. In the present study, we evaluated the safety of L-lysine added to an ordinary diet in humans. Using PubMed, Cochrane Library, Ichushi Web, and EBSCOhost as search databases, we comprehensively searched human studies on oral ingestion of L-lysine. Ultimately, 71 studies were selected for evaluation. Of these, 12 studies were of relatively high quality with Jadad scores ≥ 3. The dose range of L-lysine in the selected studies was 16.8-17,500 mg/day, and the range of dosing period was 1-1095 days. The observed adverse events were mainly subjective symptoms related to the gastrointestinal tract such as nausea, stomachache, and diarrhea. The provisional no-observed-adverse-effect level obtained based on these gastrointestinal symptoms was 6000 mg/person/day. Integrated analysis of the risk for developing gastrointestinal symptoms revealed that the risk ratio was 1.02 (95% CI, 0.96-1.07; p = 0.49); thus, no significant increase was observed. (UMIN000028914).

Lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats: a systematic review

BACKGROUND

Feline herpesvirus 1 is a highly contagious virus that affects many cats. Virus infection presents with flu-like signs and irritation of ocular and nasal regions. While cats can recover from active infections without medical treatment, examination by a veterinarian is recommended. Lysine supplementation appears to be a popular intervention (recommended by > 90 % of veterinarians in cat hospitals). We investigated the scientific merit of lysine supplementation by systematically reviewing all relevant literature.

METHODS

NCBI's PubMed database was used to search for published work on lysine and feline herpesvirus 1, as well as lysine and human herpesvirus 1. Seven studies on lysine and feline herpesvirus 1 (two in vitro studies and 5 studies with cats), and 10 publications on lysine and human herpesvirus 1 (three in vitro studies and 7 clinical trials) were included for qualitative analysis.

RESULTS

There is evidence at multiple levels that lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats. Lysine does not have any antiviral properties, but is believed to act by lowering arginine levels. However, lysine does not antagonize arginine in cats, and evidence that low intracellular arginine concentrations would inhibit viral replication is lacking. Furthermore, lowering arginine levels is highly undesirable since cats cannot synthesize this amino acid themselves. Arginine deficiency will result in hyperammonemia, which may be fatal. In vitro studies with feline herpesvirus 1 showed that lysine has no effect on the replication kinetics of the virus. Finally, and most importantly, several clinical studies with cats have shown that lysine is not effective for the prevention or the treatment of feline herpesvirus 1 infection, and some even reported increased infection frequency and disease severity in cats receiving lysine supplementation.

CONCLUSION

We recommend an immediate stop of lysine supplementation because of the complete lack of any scientific evidence for its efficacy.

Current management and recommendations for access to antiviral therapy of herpes labialis

Herpes labialis is a common skin infective condition, worldwide, which is primarily caused by HSV-1. Recurrent episodes of herpes labialis, also known as cold sores, can be frequent, painful, long-lasting and disfiguring for infected patients. At present, there are two types of antivirals for the treatment of herpes labialis, topical and oral, which are available over the counter or as prescription-only. The aim of antiviral therapy is to block viral replication to enable shortening the duration of symptoms and to accelerate healing of the lesions associated with herpes labialis. This review examines the evidence for the effectiveness of current topical and oral antivirals in the management of recurrent episodes of herpes labialis. In most countries, oral antivirals for herpes labialis are available as prescription-only. However, in early 2010, the oral antiviral famciclovir was reclassified from prescription-only medicine to pharmacist-controlled status in New Zealand. The benefits and risks associated with moving an antiviral therapy for herpes labialis from prescription-only to pharmacist-controlled status are reviewed here, and the implications for patients, general physicians and pharmacists are considered.

Could lysine supplementation prevent Alzheimer's dementia? A novel hypothesis

There is a growing body of evidence that implicates the herpes simplex type 1 virus (HSV-1) in the development of Alzheimer's dementia (AD). HSV-1 has been found to be present in the cerebrum of the great majority of older adults, and in many of the same areas of the brain that are affected by AD. When active, the virus may contribute to the formation of the neuro-fibrillary tangles and amyloid plaques characteristic of AD. Like AD, HSV-1 encephalitis may cause long term memory loss. HSV-1 replication is suppressed in lysine-rich/arginine - poor environments, and population studies suggest that diets high in lysine and low in arginine may be associated with lower rates of AD. There are no prospective studies of the efficacy of lysine supplementation to prevent or reduce the incidence of AD. Supplementation with adequate doses of lysine could prevent the development of AD.

Effect of oral administration of L-lysine on conjunctivitis caused by feline herpesvirus in cats

OBJECTIVE

To determine whether oral administration of L-lysine to cats would lessen the severity of conjunctivitis caused by feline herpesvirus (FHV-1).

ANIMALS

8 healthy young adult cats.

PROCEDURE

Cats received oral administration of lysine monohydrochloride (500 mg, q 12 h) or placebo (lactose) beginning 6 hours prior to inoculation of virus. The left conjunctival sac received a 50-microl suspension of FHV-1 grown in cell culture (1.8 X 10(8) tissue culture infective dose50) on day 1. Cats were evaluated and scores given for clinical signs each day for 21 days. Samples for virus isolation were collected from the eye and throat every third day. Plasma lysine and arginine concentrations were measured prior to the study and on days 3, 14, and 22.

RESULTS

Cats that received lysine had less severe conjunctivitis than cats that received placebo. Virus isolation results did not differ between the groups. Plasma lysine concentration was significantly higher in cats that received lysine, compared with control cats, whereas plasma arginine concentrations did not differ between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Oral administration of 500 mg of lysine to cats was well tolerated and resulted in less severe manifestations of conjunctivitis caused by FHV-1, compared with cats that received placebo. Oral administration of lysine may be helpful in early treatment for FHV-1 infection by lessening the severity of disease.

Lysine as a prophylactic agent in the treatment of recurrent herpes simplex labialis

The amino acid lysine is an agent that has been proposed for treating the clinical symptoms of recurrent herpes simplex labialis. This study examined the efficacy of long-term prophylactic lysine supplementation. Twenty-six volunteers with a history of frequently recurring herpetic lesions completed a 12-month double-blind crossovers study. The experimental group received daily oral supplements of 1,000 mg 1-lysine. Serum samples were analyzed at scheduled intervals. In most instances, members of the lysine group reported significantly fewer lesions than the control group. Similarly, those who were taken off lysine supplementation generally showed a significant increase in lesion frequency. Quantitative hematologic measurements revealed the most clinically useful relationship. Data from this sample population indicated that when a person's serum lysine concentration exceeded 165 nmol/ml there was a corresponding significant decrease in recurrence rate. Conversely, the frequency rate increased significantly as concentration levels fell below 165 nmol/ml. These results suggest that prophylactic lysine may be useful in managing selected cases of recurrent herpes simplex labialis if serum lysine levels can be maintained at adequate concentrations.

Effect of acyclovir, bromovinyldeoxyuridine, vidarabine, and L-lysine on latent ganglionic herpes simplex virus in vitro

Vidarabine and L-lysine did not prevent the in vitro reactivation of latent herpes simplex virus or block the further multiplication of reactivated latent virus. Acyclovir and bromovinyldeoxyuridine both blocked the reaction and the multiplication of reactivated latent virus, and transiently suppressed but did not eliminate latent virus from the sensory ganglia.