US Equestrian (USEF) has announced important updates to its competition medication rules, making cetirizine (commonly known by the human brand name Zyrtecยฎ) a permitted substance in USEF-licensed competition and issuing revised withdrawal recommendations for methocarbamol (Robaxinยฎ).
The changes took effect immediately and are intended to address questions raised by veterinarians, trainers, and competitors regarding the use of these commonly prescribed therapeutic medications.
Cetirizine Is Now Permitted in Competition
One of the most significant changes involves cetirizine, a second-generation antihistamine frequently prescribed to horses suffering from seasonal allergies, hives, and other allergic skin conditions.
Until now, competitors using cetirizine were required to:
- Discontinue the medication at least 24 hours before competition.
- Submit a USEF Medication Report Form.
- Comply with prohibited substance regulations.
Effective immediately, cetirizine is now classified as a permitted substance, meaning horses may remain on the medication during USEF-licensed competitions without requiring a Medication Report Form or facing medication penalties.
According to USEF, cetirizine differs from first-generation antihistamines because it does not readily cross the blood-brain barrier and therefore does not appear to cause the sedative effects that could impact performance.
Hydroxyzine Remains a Prohibited Medication
Although cetirizine is now permitted, hydroxyzine remains a prohibited substance under USEF rules.
Hydroxyzine is a first-generation antihistamine and is metabolized into cetirizine within the horse’s body. Despite their relationship, USEF will continue regulating the two medications differently.
Competitors using hydroxyzine must still:
- Observe a minimum 24-hour withdrawal period before competition.
- Submit the appropriate Medication Report Form in accordance with USEF Rule GR411.
Why USEF Made the Change
In the announcement, Dr. Stephen Schumacher, USEF Chief Veterinary Officer, explained that the decision was made after listening to member concerns about managing horses with allergies during the competition season.
“We’ve heard from our membership and understand the challenges of managing competition horses who struggle with hives and other types of allergy issues without their daily dose of cetirizine.”
Dr. Schumacher also noted that environmental and climate changes have contributed to increasing allergy challenges for many horses, making continued treatment an important welfare consideration.
The updated classification was approved by the USEF Veterinary Committee, and the USEF Board of Directors was notified of the change in July.
Updated Methocarbamol Withdrawal Recommendations
USEF also announced revised guidance for methocarbamol, a medication commonly used to treat muscle spasms and musculoskeletal discomfort.
The recommended dosage remains unchanged at:
- 500 mg per 100 pounds of body weight, administered either orally or intravenously.
However, USEF now recommends two different withdrawal periods depending on the horse’s overall treatment program.
12-Hour Withdrawal
A 12-hour withdrawal remains appropriate when:
- Methocarbamol is the only medication being administered.
- The horse is not receiving any dietary supplements.
24-Hour Withdrawal
USEF now recommends a 24-hour withdrawal when the horse is receiving:
- Any additional medication.
- Any dietary supplement alongside methocarbamol.
Why the Recommendation Changed
USEF says practitioners have expressed concerns that certain medications or supplements may influence how quickly methocarbamol is metabolized.
Although no published research currently demonstrates that these combinations increase the likelihood of a positive drug test, the Federation believes a more conservative recommendation provides competitors with an additional margin of safety until more data becomes available.
USEF also notes that several factors can influence how methocarbamol behaves in the body, including:
- Feed consumption when oral formulations are used.
- Differences between compounded products.
- Route of administration (oral versus intravenous).
While methocarbamol is widely recognized as a muscle relaxant, it can also produce side effects including:
- Lethargy
- Muscle weakness
- Ataxia (loss of coordination)
These factors make proper withdrawal timing especially important before competition.
What This Means for Competitors
For many owners whose horses require daily allergy management, the cetirizine update removes an administrative hurdle and allows treatment to continue throughout competition.
Competitors using methocarbamol, however, should carefully review their horse’s medication and supplement program with their veterinarian to determine whether the new 24-hour withdrawal recommendation applies.
Remaining current with USEF medication regulations helps protect horse welfare while reducing the risk of inadvertent medication violations.
Learn More
USEF has published additional resources explaining these updates:
- Official USEF Press Release: https://www.usef.org/media/press-releases/us-equestrian-releases-new-guidance-for
- USEF Insider: Taking a Closer Look at Methocarbamol: https://www.usef.org/media/newsletter/the-insider/taking-closer-look-at-methocarbamol
Author: Una
Una moved to Colorado in 2007 and started the Colorado Horse Forum as a way to meet other equestrians in the area. Una now rides and competes in dressage. She operates a small dressage horse breeding program in Castle Rock.
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