Performance-Enhancing Drugs in Horse Racing: What Trainers Use and Why It Matters

Last updated: July 28, 2026

By: Miles HenryFact Checked

Drug use in horse racing is a bigger issue than steroids alone. Regulators have also dealt with blood-doping agents, pain-masking medications, stimulants, and newer muscle-growth drugs such as Zilpaterol. Testing and enforcement are stricter under HISA today, but the financial pressure to win means performance-enhancing drugs remain an ongoing concern.

Are Racehorses Given Steroids?

Yes. Anabolic steroids have been used in horse racing, although they’re prohibited in essentially every racing jurisdiction today. Their appeal is obvious: they increase muscle mass, speed up recovery between workouts, and can make a horse appear stronger and tougher than it really is. But I’ve seen the downside too — a horse can look like a picture on the shedrow and still be carrying problems you won’t see until it’s too late.

The most commonly detected compounds are stanozolol, nandrolone, and boldenone — synthetic testosterone variants that build muscle and can dull the pain signals that would otherwise tell a trainer to back off. What concerns me as an owner is that the payoff looks straightforward on the surface: a bigger, stronger-looking horse that trains harder and recovers faster between works. The risk that gets buried under that upside is the masking effect. A horse that should be pulled from training keeps working because the pain that would normally stop it isn’t registering the way it should.

Do Steroids Make Racehorses Faster?

Not in the simple way many people think. Steroids don’t turn an average horse into a champion overnight. Their real attraction is that they can increase muscle development, improve recovery, and let a horse train harder than it otherwise could. The danger is that the horse may look and train stronger while whatever’s actually wrong with it is still sitting there, just less obvious.

What Types of Drugs Do Trainers Actually Use on Racehorses?

Drugs used on racehorses fall into a handful of buckets, and each one has a different reason for showing up in a barn. Some are used to build muscle, some to hide pain, some to drop weight, and some to open up the airways. Once you know what each type is actually for, it’s easier to understand why trainers reach for them and why catching them isn’t as simple as it sounds.

Anabolic Steroids — The Most Common Category

Anabolic steroids remain the most widely detected class of PEDs in horse racing worldwide. Their appeal is straightforward: they increase muscle mass, improve recovery between workouts and races, and can reduce the severity of minor injuries enough that a horse continues competing when it should be rested. The masking effect on injuries is arguably more dangerous than the performance enhancement — a horse that should be pulled from training continues to work because the pain signal is suppressed, accumulating damage that eventually produces a catastrophic breakdown.

This video covers the Bob Baffert case and the broader debate about how racing’s regulatory bodies handle repeat violations.

Is Lasix a Performance-Enhancing Drug or Just a Treatment?

No drug in horse racing generates more legitimate debate than furosemide, sold under the brand name Lasix. It is a diuretic used to treat exercise-induced pulmonary hemorrhage (EIPH) — a condition where a horse’s lungs bleed during intense exercise. EIPH is genuinely common in racehorses, and furosemide genuinely reduces its severity by lowering blood pressure in the pulmonary vessels during peak exertion.

The controversy has two parts. First, furosemide causes horses to urinate heavily before a race, reducing body weight by 20 to 30 pounds — a meaningful performance advantage at race pace that exists independent of any EIPH treatment benefit. Second, the drug’s diuretic effect accelerates the clearance of other prohibited substances from a horse’s urine, potentially masking violations that would otherwise be detected. These concerns have led most international racing jurisdictions to ban furosemide entirely. The United States continues to permit its use, with horses required to receive the drug no more than four hours before a race under veterinary supervision.

What Is Zilpaterol and Why Are Quarter Horses Getting Hurt by It?

At the Louisiana Racing Commission meeting I attended, Zilpaterol was the drug appearing most frequently in positive tests — and every case involved a Quarter Horse trainer. That’s what got my attention, because this wasn’t random noise. Zilpaterol is a beta-agonist originally developed for use in cattle to promote rapid muscle growth before slaughter. Its application in horse racing is a direct transfer of that mechanism: trainers are using it to add muscle mass and improve short-distance sprinting power in Quarter Horses, where races are decided over 220 to 440 yards and raw explosive strength is the primary determinant of outcome.

The Zilpaterol cases at Louisiana meets represent a broader pattern in Quarter Horse racing, where the extreme short-distance format creates particularly strong incentives for muscle-enhancing agents. The sport’s governing bodies have been slower to develop detection protocols for newer beta-agonists than for traditional anabolic steroids, which has allowed Zilpaterol use to spread before testing caught up with it.

How Horse Racing Tests for Drugs Today

Before 2023, horse racing in the US ran under 38 different sets of state racing commission rules — a substance banned in Kentucky might be permitted in Louisiana, and a trainer suspended in one state could simply move to another. The Horseracing Integrity and Safety Authority (HISA) changed that: it’s a uniform federal anti-doping and medication control program that standardizes prohibited substance lists, testing protocols, withdrawal times, and penalties across every state at once. A trainer suspended under HISA can’t just cross state lines to keep racing.

For the trainers in that Louisiana commission meeting room — the repeat offenders who had bounced between jurisdictions for years — HISA represents a genuine shift in consequences. Penalties under HISA also run more severe than what most state commissions were handing out, with five-year suspensions now a realistic outcome for serious violations.

What Owners Should Know About Drug Use Before Claiming or Buying a Racehorse

As an owner, the thing that concerns me most isn’t just whether a drug makes a horse run faster. It’s whether somebody has propped that horse up long enough to sell me a problem instead of a prospect. Before I claim a horse, I care less about a single race result and more about the story behind the horse. If you’re claiming or buying, a few habits go a long way toward protecting you.

• Ask about the barn’s medication policy directly. A trainer who’s straightforward about what and when they medicate is a different proposition than one who deflects the question.
• Understand withdrawal periods. Legitimate therapeutic medications have required windows before a horse can race clean — know what those look like for common treatments.
• Review veterinary records when you can get them. A pattern of repeated joint injections or unusual treatment frequency is worth asking about.
• Know the difference between treatment and enhancement. A horse legitimately treated for a real condition is not the same as a horse being propped up to finish a race it shouldn’t be running.
• Ask about previous violations. A barn with repeated steroid or Zilpaterol violations is a real red flag, not just paperwork. I’ve seen horses out of those barns look good enough to justify a big price, then go off form or get hurt in the next cycle — the past performances on paper don’t show you what’s actually been in the syringe.

What I’d Watch for in the Barn

In my experience, the horse usually tells the truth if you know how to look at it. I watch for a horse that suddenly comes back with a big jump in topline or hindquarter muscle without a real change in training or condition. That’s not always feed and turnout doing the work. I also pay attention to how a horse looks coming off a layoff — if it comes back noticeably bigger, tighter, or more filled out than it left, I start asking questions, not making excuses.

Why Do Racehorse Drug Problems Keep Coming Back?

HISA solves the jurisdiction problem, but it doesn’t solve the underlying incentive problem. At the claiming and allowance levels especially, where margins are thin and purses matter to the bottom line, the money on the table stays big enough relative to the odds of getting caught that some trainers keep taking the risk. The frustrating part for owners and fans is that testing is always chasing the next drug. That’s been true in racing as long as I’ve been around it. By the time regulators figure out how to catch one substance, someone’s already looking for the next shortcut — which is exactly what Zilpaterol showed at Louisiana Quarter Horse meets.

International consistency remains an issue as well. A horse trained in a jurisdiction with looser rules, imported for a major American race, may carry substances that cleared testing in its home country but would be prohibited under HISA. The protocols for managing international entries are significantly more complex than domestic testing, and elite international races continue to present regulatory gaps that sophisticated operations can exploit.

FAQs About Drugs and Steroids in Horse Racing