I saw you had posted and asked about L-Lysine for FIV cats specifically w/ upper respiratory. I have an FIV cat and was instructed by my vet to give him L-Lysine to help boost his immune system. I use the Solaray brand (bought online at The Vitamin Shoppe or Amazon.com - cheapest prices) and he gets half of a 500 mg capsule sprinkled on his food once a day. No taste so he accepts it readily. He now just has a clear runny nose from time to time but no infections. Just an FYI,,, ~Renee