You can find lysine in three different forms- hard capsule, which is pretty difficult to give a cat, or in a powder in a gel cap, and in a gel form. You can almost always find it at health food stores, and I have found the best prices at the chain vitamin world, b/c they have deals with by one get one 1/2 off. I found the gel form through my vet, but I found it pretty difficult to give rocky. Since my cats "share food bowls" and I have younger cats that I wanted to boost immunity so they didn't end up it the herpes like rocky, plus another cat that had a cold around the same time, I have been giving lysine to all four. I give each cat 1/2 capsule twice a day mixed in with 1/4 can wet food, so they each get approx 500 mg. I go through 1 pill a day per cat. I suppose I can dispose with giving the rest of the cats the lysine pretty soon, the babies are 9 months old, and zakk has been over the cold for 3 months, but the problem is that you can't tell a cat to only eat out of one dish, and it can't hurt the rest of them.