The explanation for Kentucky Derby winner Medina Spirit failing the race day drug test is that one of the grooms (horse attendants) drank cough syrup, urinated on some hay, and the horse ate the hay.

This perfectly plausible chain of events resulted in the horse having more than twice the allowed amount of betamethasone (corticosteroid) in its blood.

How much betamethasone syrup would someone have to drink for the excreted amount to pop in a half-ton horse?

(The fact that betamethasone syrup is not prescribed for coughs is something we'll let his attorneys worry about).