This is a long article, but truly an important read. I've often wondered about using Convenia (an injectable antibiotic) and had some reservations about using it. Please read this and you'll also find some very helpful tips on how to pill your cat, general rules of when to use or not use antibiotics (not after a dental!). Dr. Pierson is highly regarded in her field and is a must-read for any cat mama/papa.
http://www.catinfo.org/?link=convenia