We had a sheep ate rhododendron leaves (similar, I believe). Vet said nothing worked against the toxin, it all depended how much had been eaten compared to bodyweight. He could only alleviate symptoms - antibiotic, steroids, vitamins and we gave charcoal ground up in strong black tea. The charcoal helps absorb the toxins, I beleive, and the caffeine in the tea acts as a stimulant.
The sheep survived btw.