Kathy, I am so sorry to here about Winston. Poor guy.
Do you have a holistic vet near you? I ask because my holistic vet can offer up some Chinese herbs that work better than traditional medicine. My vet gives us Early Comfort - this herbal has remedied the worst bloody diarrhea, etc
This page lists the herbs in the product
Kan Herbals - Individual Product Information
It is something humans can use, the dogs have it in small doses. I just keep it on hand now, as I have seen how well it works