Vetoquinol Care Enisyl-F when the resistance can use a boost, especially against viruses like cat flu. Care Enisyl-F for kittens and cats is an animal feed supplement in the form of a paste with L-Lysine. This is an essential amino acid that needs to be ingested with the feed. Sick or recovering animals use more L-Lysine than regular. It is in a convenient pump package and can be administered directly into the mouth or mixed with the feed. If the cat does not accept it, you can wipe the paste on its paw, and it will be compelled to clean its paw by licking it.