Here is a link to the story.  There was problem with the drug the horses were given.  It is interesting to note in the story, that this particular drug is not approved for us in the U.S.

http://apnews1.iwon.com//article/20090423/D97O9HHG1.html

http://news.yahoo.com/s/ap/20090423/ap_on_re_us/us_dead_polo_horses

Why did they have to have something "special" that had to be mixed up by a pharmacy in the first place?

Looks to me like the very best feeds and supplements legally available in the US would be good enough.

The US has some great equine supplements.  I'm sure the vet could have recommended some supplements that were close to what they have been using.  I would not think anyone would have to make up a batch of medicine.  It does look bad, since they are on US grounds, their horses are dead, it is our vets and pharmacy.  I feel bad for the animals, owners, riders, vet tech(s) that helped the animals.  You can never replace what is gone forever.   

OK, so they played by the rules technically.  They couldn't use that drug so they had a pharmacy recreate it...rule bending at the least.  The US polo association doesn't test for drugs, so they wouldn't have been caught if they had just used the real supplement.  If the 'drug' gave horses an advantage the racing world would be all over it, yet they wouldn't test for the chemicals in this supplement which tells me it really isn't going to give horses 'the edge' in competition.

Sounds to me like everyone is at fault here: the team for going around the rules, the vet for writing the script and the pharmacy for not checking their math (Yes children, unit conversion is important.)

I wonder if they'll collect insurance on this little error that cost those ponies their lives?