ivermectin?

a vet friend of mine told me about ivermectin for use on our bantams for internal parasites and that we could use it as a preventative.
lookig at the literature on the box/bottle it says its not licenced for poultry.
does anyone have any ideas or thoughts? another person told me that it could produce feather drop and not allow feathers to regrow - is that true?
help please.

I use it regularly, first introduced to me for its delousing properties for Polands, who are very prone to crest mite. I think it is fab