Rompun® for Horses: Dosage, Dosage Chart, Precautions & Everything Owners Should Know (100 mg/mL)

Written & Reviewed By: Medshorse Team
Last Updated: October 2026

Rompun for horses is a prescription sedative and pain reliever (xylazine). The FDA label dose of Rompun 100 mg/mL is IV–0.5 mL/100 lbs (0.5 mg/lb) & IM–1.0 mL/100 lbs(1.0 mg/lb).

A 1,000 lb horse therefore gets 5 mL IV or 10 mL IM. That is the label dose, not a prescription for your horse. Your veterinarian decides the actual dose.

Why does this matter so much? Rompun 100 mg/mL is a concentrated product. A decimal slip or a mix-up with a weaker xylazine product can turn a calm horse into a dangerous situation.

This guide walks through what Rompun does, the label dosage chart, what to watch for, and the mistakes worth avoiding. It is for education and does not replace your vet’s instructions.

Quick safety note: Rompun is a prescription drug. Federal law restricts it to use by or on the order of a licensed veterinarian.

Quick Facts

Rompun® (xylazine) 100 mg/mL for Horses

Drug class

Sedative, analgesic, muscle relaxant

Label dose (IV)

0.5 mL / 100 lb

Label dose (IM)

1.0 mL / 100 lb

Onset

3–5 min IV · 10–15 min IM

Sedation lasts

Usually 1–2 hours

Pain relief lasts

15–30 minutes

⚠ Prescription only. Not for horses intended for human consumption. Not for human use.

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Disclaimer: For educational use only. Rompun is a prescription drug and must be dosed by or under the direction of a licensed veterinarian. Always confirm the dose against the current product label for the species and concentration being used.

What Is Rompun for Horses?

Rompun is the brand name of xylazine injection from Dechra Veterinary Products. It sedates the horse, relaxes its muscles, and gives short-lived pain relief.

The FDA-approved 100 mg/mL version comes in a 50 mL multi-dose vial. It is approved under NADA 047-956 and sold only through veterinarians.

Xylazine belongs to a drug family called alpha-2 adrenergic agonists. It calms the central nervous system, which is why horses often stand quietly with a lowered head after an injection. According to the label, Rompun is non-narcotic.

Two things worth knowing up front:

The 100 mg/mL strength is the one in this guide. Other xylazine products come in weaker concentrations, so a mL of one is not a mL of another.

What Is Rompun Used For in Horses?

Vets use Rompun to calm a horse enough for an exam or procedure, and to relieve pain for a short time.

The label lists these uses in horses:

Diagnostic work: oral and eye exams, rectal and abdominal palpation, bladder catheterization, radiographs
Orthopedic procedures such as applying casts and splints
Dental procedures
Minor surgery of short duration, such as wound debridement, removing skin growths, and suturing lacerations
Calming fractious or difficult horses
Sedation and pain relief after injury or surgery
A preanesthetic before general anesthesia, or with local anesthetics such as lidocaine or procaine

In practice, many owners meet Rompun during emergencies and routine visits. A common example is a painful colic episode.

If you are managing one, our guide to Banamine covers the anti-inflammatory side, but never give anything without your vet's go-ahead.

Rompun Dosage for Horses (100 mg/mL)

The FDA label gives two routes. Intravenous (IV) is 0.5 mL per 100 lb of body weight. Intramuscular (IM) is 1.0 mL per 100 lb.

In milligrams, that is 0.5 mg/lb IV and 1.0 mg/lb IM. In metric terms, it is roughly 1.1 mg/kg IV and 2.2 mg/kg IM.

The IM dose is double the IV dose. This is normal, because intramuscular absorption is slower and less complete. Never swap one for the other.

Rompun Dosage Chart for Horses by Weight

Rompun® 100 mg/mL: Label Dose by Body Weight

Weight (lb)	≈ kg	IV dose (mL)	IV (mg)	IM dose (mL)	IM (mg)
100	45	0.5	50	1.0	100
300	136	1.5	150	3.0	300
500	227	2.5	250	5.0	500
700	318	3.5	350	7.0	700
800	363	4.0	400	8.0	800
900	408	4.5	450	9.0	900
1,000	454	5.0	500	10.0	1,000
1,100	499	5.5	550	11.0	1,100
1,200	544	6.0	600	12.0	1,200
1,400	635	7.0	700	14.0	1,400
1,600	726	8.0	800	16.0	1,600

How this was built: IV = 0.5 mL per 100 lb; IM = 1.0 mL per 100 lb (FDA label, NADA 047-956). This chart applies to the 100 mg/mL product only. Your vet may use a different dose for your horse. This is not a prescription.

How to Calculate Rompun Dose (Worked Example)

Divide the horse's weight by 100, then multiply by 0.5 for IV or by 1.0 for IM.

Take a 1,200 lb horse:

1,200 ÷ 100 = 12
IV: 12 × 0.5 mL = 6.0 mL
IM: 12 × 1.0 mL = 12.0 mL

Dose Math in 3 Steps (100 mg/mL)

Get accurate weight

Use a scale if you can. Weight tapes can be off.

Divide by 100

1,200 lb ÷ 100 = 12

Multiply by route

IV: 12 × 0.5 = 6 mL
IM: 12 × 1.0 = 12 mL

Always double-check: have your vet confirm the volume before anything is drawn up.

Can You Give Rompun by Mouth or Under the Skin?

No. The label lists only intravenous and intramuscular routes.

Any other route is outside the label. Subcutaneous or oral administration is not described in the label for horses, so your vet's instructions should always come first.

Do Vets Always Use the Full Label Dose?

Not always. The label gives the reference dose for sedation of 1 to 2 hours. In real practice, vets tailor doses to the horse's temperament, health, and the procedure.

A lighter sedation for a short exam may use less. This is a clinical judgment, and it is why you should never repeat or adjust a dose on your own.

How Fast Does Rompun Work and How Long Does It Last?

Rompun works in 3 to 5 minutes after IV injection and in 10 to 15 minutes after IM injection. Sedation usually lasts 1 to 2 hours, but pain relief lasts only 15 to 30 minutes.

What to Expect After Injection

IV (vein)

Pain relief 15–30 min

Sedation continues up to ~1–2 hours

Onset 3–5 min

IM (muscle)

Pain relief

Sedation continues up to ~1–2 hours

Onset 10–15 min

Bar lengths are illustrative. Timings come from the FDA label; individual horses vary.

Rompun Side Effects in Horses

At label doses, Rompun can cause muscle tremors, a slower heart rate (bradycardia) with partial AV block, a lower breathing rate, and sweating.

The label also notes that a sedated horse may still react to sharp sounds. Here is what each effect means:

Slow heart rate and partial AV block: The label says this resembles the AV block seen in normal horses. It is reported more often after IV than IM injection. The label notes that atropine, given before or after Rompun, greatly reduces the incidence. That is your vet's call.
Reduced breathing rate: This is expected, as in natural sleep. It matters more in horses with respiratory problems.
Blood pressure shift: IV use causes a brief rise, followed by a slight drop.
Sweating: Rarely heavy.
Muscle tremors: Occasional and slight.

When to call your vet immediately: collapse, seizure-like activity, labored breathing, a very slow or irregular pulse, or a horse that cannot stand and does not recover as expected.

⛔ Use extra caution (label)

Significantly depressed breathing
Severe heart disease
Advanced liver or kidney disease
Severe endotoxic or traumatic shock
Stress: extreme heat, cold, high altitude, fatigue
Combination with tranquilizers (label says don't)

✅ Handler safety

Keep quiet; noise can trigger a defensive reaction
Never assume a sedated horse can't kick
Avoid injecting into the carotid artery
Keep out of reach of children
Avoid skin, eye and mouth contact
Wash exposed skin or eyes with water

Key Precautions

1. Avoid the carotid artery

The label warns that accidental injection into the carotid artery can cause immediate violent seizures followed by collapse. Recovery can be rapid and complete, but your vet needs to confirm the needle is in the jugular vein.

2. A sedated horse is not a safe horse

The label states that a heavily sedated-looking animal can still respond defensively to handling or sudden noise. Stand to the side, stay calm, and keep other people out of the kicking zone.

Pain relief can be patchy. The label notes analgesia varies and is most variable at the distal limbs. Your vet will test the depth of sedation before starting.

3. Do not use it with tranquilizers

The label says not to use Rompun in conjunction with tranquilizers. That includes acepromazine, a phenothiazine tranquilizer. If your vet plans a combination, that decision belongs to them.

4. Be cautious with barbiturates

The label explains that Rompun adds to the effect of barbiturates such as pentobarbital and thiopental, so those drugs need lower doses.

Typically, only 1/3 to 1/2 of the calculated barbiturate dose is needed. This is anesthesia territory and is strictly for veterinarians.

5. Transporting a sedated horse

The label says transport works best once the full effect is reached and the horse is stable on its feet. Noise or stimuli can still arouse the horse and raise the risk of injury.

5. Pregnancy and lactation

The horse label does not give specific guidance for pregnant mares. Ask your vet. For people, the label warns that pregnant women should take special care to avoid self-injection because uterine contractions and decreased fetal blood pressure may occur after accidental systemic exposure.

Is Rompun Safe for People Who Handle It?

No. Rompun is not for human use, and accidental self-injection is a medical emergency.

The label's human safety warnings say:

Avoid self-injection, oral intake, and any contact with skin, eyes, or mucous membranes.
After accidental injection or swallowing, seek medical advice immediately, show the package insert, and do not drive.
Wash skin or eyes with plenty of water after contact.
People with cardiovascular disease (such as high blood pressure or ischemic heart disease) should take special care to avoid any exposure.

Xylazine can cause breathing depression, slow heart rate, low blood pressure, dry mouth, and high blood sugar in people. Dechra's number for adverse reactions and the SDS is 1-866-933-2472.

Competition Horses and Food Animals

Rompun must not be used in horses intended for human consumption. The label says so directly.

For competition horses, medication rules vary by organization (for example USEF or FEI). I could not find a publicly stated detection time on the label, so I won't guess one.

Ask your vet and check your governing body's current medication rules before an event.

Rompun vs Dormosedan vs Acepromazine

All three calm horses, but they are different drugs with different jobs. Rompun (xylazine) and Dormosedan (detomidine) are both alpha-2 agonists with sedative and pain-relieving effects. Acepromazine is a tranquilizer that sedates but does not provide pain relief.

Equine Sedatives Compared

Feature	Rompun (xylazine)	Dormosedan (detomidine)	Acepromazine
Drug class	Alpha-2 agonist	Alpha-2 agonist	Phenothiazine tranquilizer
Sedation	Yes	Yes	Yes
Pain relief	Yes (short, 15–30 min)	Yes	No
Combine with Rompun?	—	Only if your vet directs	Label says not to use Rompun with tranquilizers

Rompun details from the FDA label. Choice of drug depends on the horse and procedure; this is a general comparison, not a recommendation.

Rompun Dosage Mistakes to Avoid

Mixing up concentrations. Different xylazine products have different strengths. A volume that is right for a weaker product could be a serious overdose with 100 mg/mL.
Confusing IV and IM. The IM dose is double the IV dose. Drawing up the wrong one is a dosing error.
Guessing weight. An inaccurate estimate leads directly to an inaccurate dose. Weigh the horse or use the best measurement you have.
Re-dosing early. Wait for the full effect before deciding anything. Let your vet make the call.
Treating a "sleepy" horse as harmless. The label warns about defensive reactions.
Combining with other sedatives without guidance. The label advises against tranquilizers and urges caution with barbiturates.
Using a vial that is too old. The label says to use within 30 days of first puncture and puncture a maximum of 20 times. Discard anything beyond that.

Storage and Handling

Store Rompun at 68°F to 77°F (20°C to 25°C). Do not freeze it. The label allows brief excursions up to 104°F (40°C). Keep it locked away from children, and never reuse a vial past 30 days after first puncture or 20 punctures.

Key Takeaways

Label dose: 0.5 mL/100 lb IV or 1.0 mL/100 lb IM (100 mg/mL).
Onset: 3–5 min IV, 10–15 min IM. Sedation 1–2 hours. Pain relief 15–30 minutes.
Never use it in horses meant for human consumption, and never use it in people.
Avoid the carotid artery and avoid combining with tranquilizers.
Check the concentration every time, and let your vet set the dose.

FAQs

What is Rompun used for in horses?

It sedates, relaxes muscles, and gives short-term pain relief for exams, dental work, minor surgery, handling difficult horses, and as a preanesthetic.

How much Rompun for a 1,000 lb horse?

At label doses, 5 mL IV or 10 mL IM of the 100 mg/mL product. Your vet decides the actual dose.

How long does Rompun take to work?

About 3 to 5 minutes IV and 10 to 15 minutes IM.

How long does Rompun last in a horse?

Sedation usually lasts 1 to 2 hours. Pain relief lasts 15 to 30 minutes.

Is Rompun the same as xylazine?

Yes. Rompun is the Dechra brand name for xylazine injection.

Can I give Rompun to my horse without a vet?

No. It is a prescription drug restricted to use by or on the order of a licensed veterinarian.

Can Rompun be given orally?

The label lists only IV and IM routes.

My Final Thoughts

Rompun is an effective, widely used tool when it is dosed correctly and handled with respect. Know your horse's weight, confirm the concentration, stay out of the kicking zone, and let your vet lead.

Next steps: save the dosage chart, ask your vet to confirm the plan before any procedure, and read about related medications such as bute dosage for horses and Banamine dosage for horses.

Medical disclaimer: This article is for education only and does not replace professional veterinary advice. Doses here are drawn from the FDA label and may differ from what your veterinarian prescribes.

Sources:

DailyMed, Rompun (xylazine injection) 100 mg/mL, Dechra Vet Products, revised 12/2025, NADA 047-956 (dailymed.nlm.nih.gov); Dechra US Rompun product page; FDA reporting of animal drug adverse events (fda.gov/reportanimalae).