Plasma lysine and arginine levels were determined at baseline, during and at the end of the study. However, only 3 measurements were taken, which does not allow extrapolation of the data to the complete study period (52 days). A previous study by Maggs et al.  showed that plasma lysine was elevated only 2–3 h after ingestion. Unfortunately, no information was given about the moment of blood collection of the 3 samples in this study. At day 17 and at the end of the study at day 52, plasma lysine levels in the lysine group were elevated compared to baseline values, and 1.5–3 times higher than in the control group. Contrary to previous studies, the authors reported a decline of plasma arginine levels. However, this was observed in both groups, albeit a significantly stronger decrease in the lysine group (60 nmol/ml at the end of the study; a 40 % reduction compared to baseline values) than in the controls (80 nmol/ml; a 25 % reduction). Since plasma lysine did not increase in the control group, the decline in plasma arginine levels cannot be attributed to lysine supplementation. Contradictory to the previous, smaller studies, the authors found that ocular and upper respiratory disease were more frequent among cats receiving the lysine-rich food (88 %) as compared to the control group (60 %), and clinical signs were also more severe. The authors speculated that aggression among the male cats in the lysine group may have induced additional stress, possibly reactivating the virus. However, the clinical severity score for female cats in the lysine group was higher at all 15 measuring points throughout the study when compared to females fed the basal diet, and this difference approached statistical significance (P = 0.08). The authors did not compare the complete (male and female) control group with the females only in the lysine group. Seven cats seroconverted for FHV-1 during the study, 6 in the lysine group and 1 in the control group (which had a lower titer than all 6 cats in the lysine group, and undetectable viral DNA). FHV-1 was detected in conjunctival fluid in 7 cats on 13 occasions: 1 cat in the control group on 1 occasion and 6 cats in the lysine group on 12 occasions.
Caution When Selecting Lysine Supplements for Your Cat.
In the second study,5 14 latently infected cats received 400 mg of lysine Q 24 H PO. Viral shedding was monitored for 30 days. Lysine administration in these cats was associated with a statistically significant reduction in basal viral shedding compared with levels in cats that received placebo. Since these cats were normal, latently infected carrier cats, little or no clinical disease was seen during the month-long study in the placebo or lysine group. In both studies, plasma arginine concentrations remained in the normal range, and no signs of toxicity were observed, despite notably elevated plasma lysine concentrations in treated cats.
Which form of L-Lysine works best for your kitty
You and your cat might take the same over-the-counter supplement, if your vet treats your kitty for certain conditions. Many cats are exposed to the feline herpes virus and never show any symptoms. Before she turns her nose up at lysine treats, tell her they will make her even more beautiful. L-Lysine Supplement for the management of Feline Herpes (FHV-1) in kittens and cats Lysine administration has been shown to inhibit replication of the Feline Herpes Virus (FHV-1) and can be used in the management of FHV-1 infection. LysineAid is a very palatable and easy to give gel specifi cally for cats. For kittens give 1ml twice daily for one week before periods of stress and for at least 2 weeks afterwards. If your cat likes the taste, this is a great deal easier than trying to give your cat lysine tablets. In some countries, you can find a similar product called Viralys.
Right now the vet has me give Maxie L-lysine for her feline herpes