One year my whole lot of kitties came down in wintertime with respiratory infections (looks to me like a cold). My oldest was already taking L-lysine for his herpes with sneezing, so I figured it was worth a try. I tried it and it worked. None of them died on me.
After trial & error, the easiest way I have found to do this is... get a short/wide glass jar, put in about 30 (number doesn't matter as long as you match the correct amount of water with it) 500 mg L-lysine tablets in it, then take a syringe and put in 1cc of filtered water in it for each tablet (So, if you had a syringe that went up to 3cc's, you would only need to put in 10 of those full, and it doesn't have to be exactly perfect either.) Then leave the tablets and water sit up in the cabinet overnight with a lid on it. The next day it might turn out smooth, or it may be lumpy (I don't know why it turns out lumpy sometimes), but if it's lumpy just strain it through a metal strainer and then it will stay fine.
Now, you have 30 doses of lysine at the ready. Just take out the jar, stir it up a little, and fill the syringe up to the 1cc mark for each dose (I give mine slightly more, but wouldn't give them more than 1 & a half cc's a day. I use to have to crush a pill every time to give a dose. This is much easier and last a long time. If it starts to get cakey before you finish, you might could add a little water to it or just start over.
This method has made my life so much easier. I hope it helps someone else also.
God Bless All... GRG7 : )