12.5 mg of Benadryl is what I give for all of mine. We use it before I give boosters too. You can either give the child version or the adult which you cut into 1/2 a tablet. What I do is put the pill into a little cream cheese. The children version also has melt in the mouth which is also a good choice.
Here is a sticky will all kinds of great information and Benadryl dosage is on there too. Take a look:
http://www.yorkietalk.com/forums/sic...g-dosages.html