PromAce, Promazine Granules,Tranquazine

Acepromazine is a very useful tranquilizer that depresses the central nervous system, causing sedation, relaxation, and a reduction in involuntary movements. It does not provide any relief from pain, however, and will not prevent a horse from moving or kicking (possibly slower) if it is startled or feels pain.

Acepromazine may be used as a sedative to facilitate handling of the animal during diagnostic procedures, veterinary treatments, shipping or other situations which require a “tranquilizer.’ The veterinarian will also use acepromazine during minor or major surgical procedures alone or in combination with local or general anesthetics.

Intravenous and intramuscular administration is recommended at a dosage of 2-4 mg100 IBM of body weight. This dose will result in marked sedation, suitable for carrying out minor surgical procedures with the use of a local anesthetic. When tranquilizing horses for minor procedures, such as clipping, braiding, or for shipping, doses of 0.5-1 mgl100 Ib. of body weight will usually prove adequate and leave the horse with enough muscular coordination so that tailing is not a serious problem.


There is no oral form of acepromazine available. Oral tranquilization however can be achieved by use of a related compound, promazine hydrochloride, which comes in granules and is given along with a normal amount of teed. (See Promazine hydrochloride).

When given intravenously, full effect is reached in approximately 15 minutes. With intramuscular use, a full 30-45 minutes should be allowed (occasionally longer). For best effect, horses should be left undisturbed following administration of the drug. Peak activity lasts from 1-4 hours after administration. This will be prolonged in sensitive animals. Residual mild tranquilization is commonly observed for 12 hours or even longer after administration.

Central Nervous System: Accidental intra-arterial injection usually into the carotid artery during injections into the neck can produce signs ranging from excitement and disorientation to convulsions seizures and even death.

Acute and chronic toxicity studies show a very low level of toxicity with a wide safety margin in dosage. However, these studies refer only to the chance of death or serious organ injury. As already stated, over-sedation, causing dangerous incoordination, is a very real risk in some animals. It should also be noted that swallowing ability is impaired in heavily tranquilized animals. Horses should be muzzled or restrained on crossties with an attendant present, until they have become alert after the use of this phenothiazine tranquilizer.

A drop in blood pressure hypertension can occur in any horse if acepromazine is administered too rapidly by the intravenous route. Hypertension is also a very real risk in horses that are in poor condition (malnutrition), dehydrated, septic severe infections, in shock e.g., colic. USE OF ACEPROMAZINE UNDER ANY OF THESE CONDITIONS IS DIRECTtLY CONTRAINDICATED.

In adult male horses, acepromazine normally causes relaxation of the retractor penis muscle. This results in the penis being relaxed and dropped out other sheath. However very occasional cases have been reported where an irreversible paralysis of the retractor penis muscle has occurred, although this is more common with at least one other phenothiazine tranquilizer. This risk should be considered before giving acepromazine to an intact male horse. When used, minimum dosage recommendations should be followed.

Horseman’s Comments:

I have had couple of dozens experiences using this product in training when riding or training for other trainers in my younger days (small doses, only 1 cc). My experiences produced following observations:

In racehorses I have noticed “heavier” breathing and excessive perspiration while the product had no effect in reducing the horse’s nervousness for which the product was used . The horses also seemed to tire quicker when on this drug.

When riding and training, this drug noticeably dulled the horse’s responses and the animal was in less cooperative mood.

It was also obvious that the learning speed was noticeably reduced; as the horses were very often barely aware of what was going on, and their attention/interest to the work was greatly reduced as well.
There are alternate “calmers” that can be used in training without the abuse to the animal. More on this site.
If you believe that you can reason with a “drunk” person, then go ahead and try it with a “drunk” horse”.

If you need to use Ace for either riding or training of a horse, you are better off to get either more education or experience. Better yet, just get another horse since many horses are often “forced” into unsuitable (for them) service.


If used in place of training, it is being abused.

I try to avoid the use of this drug for:

o Riding

o Training

o Shoeing (There is a slim line between courage and foolishness).

o Loading the horse into the trailer prior proper education.

One caveat: if the horse gets upset while under the influence, the results can be pyrotechnic. (Sorta like a belligerent drunk.) (One person is happy when dunk and another angry)

o If given to already excited horse, I have noticed that the horses can put up a fierce fight, which often resulted in injuries to people and the animal alike, while the drug never achieved the purpose for which it was used to begin with. (Giving to an already angry/upset person enough alcohol to get him drunk will often result in a display of madness, Ace can do the same to a horse)

As all drugs effect horses in different ways, so does Ace. This drug will not have always the expected “calming” effect on horses. I have sometimes witnessed the “backfire” (the opposite) effect of this drug.

There is no need for using this drug when washing the horse’s sheath. It can be done quite well without the horse “hanging”.

Recommended use of Ace, according to my experiences in the following practices:
To reduce the “shipping anxiety” in the animal, but not prior proper loading education. If your horse doesn’t want to load, you should know the answer to it. That is if you have some idea what “your” horse is. More on that on our other web Stablemade Horse Care.

I have used it sometimes as an emergency treatment after horse “tied up” when there was no other drug at hand and when a Veterinarian was not available immediately. Consult your vet should your horse tie up. There can be serious complication when a horse ties up and it is never as insignificant as it appears to many folks. More on that later on this site. Ace also never worked for me if used as a preventative measure in “tying up”.

The uses for this drug are OK, as stated above in the article, for clipping ears, suturing wounds, etc. However I believe that education of the animal in many areas where the drug is used, can prevent the unnecessary usage or the abuse of Ace. Veterinarians often mix this drug with other tranquilizers for better effectiveness. No one (other than a vet) should experiment in this field.


We thank our friends at for supporting the website.