I'm not an expert, to say the least, but I would honestly call your local vet office and ask for your regular vet. If you don't have a regular vet, just ask if there's someone you can ask some questions to. They're a really good resource and you shouldn't get charged for the phone call. If you're on good terms with your vet, they probably know your horse a little better than us general forum people do. XD
I hope someone else has better information than me, but I thought I would throw that option out there.
"There's no such thing as a problem horse. Just people that cause problems for horses." - Unknown