At an inquiry held at the NHA offices in Johannesburg last week, Miller was charged with contravening rule 73.2.4, being the trainer responsible for the horse Island Mischief.
The incident happened during the running of the sixth race at the Flamingo Park Racecourse on May 20.
A blood specimen was taken from the horse and, upon analysis, the presence of Methylprednisolone, which is a prohibited substance in terms of the NHA rules, was found.
Miller pleaded guilty to the charge, and was fined R40,000 with the right to appeal against the penalty imposed.
Would you like to place a bet on the horses? Click here to get started in 3 easy steps.