Gabapentin: What Is It?

The news last week that leading trainer Saffie Joseph Jr. has been suspended for 15 days and fined $500 by the Pennsylvania Racing Commission—pending appeal—after one of his trainees tested positive for the substance gabapentin after winning a graded stake at Presque Isle Downs last September, led to a collective head scratch.

What exactly is gabapentin?

“It is a drug that is used as an anti-convulsant in people. It is also used for neurotrophic pain—in other words, pain originating from nerves,” said former California Horse Racing Board (CHRB) director, Rick Arthur. “For example, if you have shingles, they're likely to put you on gabapentin.”

According to the government run MedlinePlus website, gabapentin is commonly prescribed to help control certain types of seizures in people who have epilepsy, and works by decreasing abnormal excitement in the brain.

Common gabapentin medications include Horizant, Gralise, and Neurontin.

Its use in human medicine has increased as an alternative pain relief to highly addictive opioids, said Arthur. But “frankly, it is not very effective,” he added, of the orally administered drug. 

Gabapentin is a Class 3, penalty category B drug according to the Association of Racing Commissioners International, meaning it is deemed to have certain uses in racehorses.

Under the Horse Racing and Integrity Act's (HISA) impending anti-doping and medication control (ADMC) program, gabapentin is listed as a category B controlled substance. This means it is permitted for use in certain windows. 

When HISA's ADMC goes into effect on March 27, a first-time gabapentin positive comes with a possible 15-day suspension, a fine of up to $1,000, and automatic disqualification of the race-day results.

So, for what kinds of issues can gabapentin be used to treat in horses?

“It was advocated about 10, 15 years ago as a way to treat navicular disease,” Arthur said. “But that kind of fell apart as it didn't work.”

It is also used to treat lameness in horses, “but more as a desperation move when they don't know what it is,” he added.

Because of its use as an anti-anxiety medication in humans, some say it has the same potential off-label use for horses, too.

Neither Southern California-based private veterinarian, Ryan Carpenter, nor current CHRB equine medical director, Jeff Blea, are aware of gabapentin being used as a calming agent in racehorses. Though Blea admitted that it could have that effect. 

According to the CHRB's stewards rulings webpage, there have been roughly 18 individual gabapentin positives in California since 2005.

“For the most part, they were normally cases where the humans associated with the horse were on gabapentin,” said Arthur, explaining how most cases were ruled instances of environmental contamination.

“We have no idea how the transfer occurs. We were suspicious that it was secondary contamination from someone urinating in the stall but we never confirmed that,” he said. 

In one instance, an off-track veterinarian had prescribed gabapentin to a dog that was brought to the barn, said Arthur. 

“We assumed it was from urine,” said Arthur, when asked about how the transfer was made. “Why someone would let a dog urinate in the stall I don't know. 

While the relationship between a person or an animal prescribed gabapentin and a positive finding in a horse is clear “in most cases,” said Arthur, “there were a number of instances where there was no explanation for it other than the horse being administered gabapentin.”

According to Arthur, if the reported finding shows gabapentin at nanograms in the low single digits, that is typically an indication of environmental contamination. 

“If it's up over 15, 20 nanograms, I would expect that to be an intentional administration,” said Arthur. “We had one case around 100 nanograms, which would be impossible to explain by accidental contamination.”

The Pennsylvania Racing Commission did not publish the amount at which gabapentin was found in Artie's Princess's (We Miss Artie) post-race sample. However, Joseph told the TDN last week that the horse tested positive at a level that should be considered below the recognized threshold level.

Joseph also told the TDN that the horse was tested 24 hours before the race by the same laboratory. “The horse was negative and was then positive the next day when no vet treated her. How is that possible? The proof is in the pudding,” said Joseph. 

According to Arthur, “you would not expect this drug to work for more than 12 to 24 hours in any sense as an analgesic or pain reducing medication.”