She will receive credit for having served more than three months of a provisional suspension, imposed following confirmation of the positive test.
The case involved the horse Luke Skywalker 46, ridden by Johnson in a CSI2* jumping event in Wellington, Florida, from January 17 to 22.
Blood and urine samples were taken from the horse on January 21 for testing.
The testing revealed the presence of pramoxine, a local anaesthetic used to relieve pain and itching. It is classified as a banned substance under the FEI Equine Prohibited Substances List.
The tribunal was told that Luke, like all horses, got the occasional minor cut and a veterinarian had recommended the use of a triple antibiotic cream in such cases, which the vet had indicated was OK under the anti-doping rules provided it did not contain added corticosteroids or pain relief.
A groom, Sergio Molinero, told of going to Walmart on January 5 this year, where he took four tubes of the antibiotic cream off the shelves for purchase.
“I was buying the same triple antibiotic we always buy which is okay under the anti-doping rules. I now realize after Paige was able to find my receipt for the purchase that I made a mistake and pulled the wrong tube off the shelf because it looked so much like the one we always use,” his written submission said.
“I now see that I mistakenly bought triple antibiotic with pain relief, and the pain relief contains pramoxine.
A veterinarian, Dr John Nolan, also provided an account, saying that Johnson was meticulous about her procedures in the barn and continually demanded a higher level of caution than even he recommended.
He said he had worked with many professional equestrian athletes over the years, and he could say without reservations that Johnson was the most careful and ethical rider with whom he had ever worked.
He confirmed that he had advised Molinero that he may use a triple antibiotic on the horse, “but he should avoid any corticosteroid or pain relief in the ointment.”
Regarding fault, Johnson, represented by Lisa Lazarus, argued that she did not breach any duty of care. The evidence showed that her policies and procedures involved an exceptionally high level of care and responsibility, as confirmed by Nolan.
Johnson’s suspension will end on April 4, 2018.