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By Stephen Reed, DVM, Dipl. ACVIM

Chances are you've haven't heard much about the drug Buscopan (N-butylscopolammonium bromide). Although it has been used in Europe for many years to treat gastro-intestinal cramping in people and animals, Buscopan only became available in this country in 2001, when it was approved for veterinary applications. Nonetheless, you'll probably be hearing more about this medication in the coming years as U.S. practitioners become more familiar with it.

Buscopan is an antispasmodic that acts specifically on smooth muscles, such as those in the digestive system and reproductive tract. This makes it particularly effective in relieving gas colics, which are charaterized by severe, painful cramping of the muscles lining the intestines. In the process, Buscopan essentially stops gut action for a short time less than a half-hour but that downtime often serves to "reboot" the gut and restore normal activity.

The pain relief associated with Buscopan comes from relaxation of muscle spasms rather than any analgesic properties. This makes it safer than some of the other first-line colic medications that mask pain, which can give the impression the horse is improving when, in reality, he may be getting worse. In other words, a horse with serious, surgical colic- such as a twisted gut - will not feel any better if given Buscopan. In fact, some veterinarians administer the drug as a diagnostic procedure to determine the severity of a colic.

Buscopan also has other uses. It can relax a mare's uterus so that a veterinarian can reposition a foal during delivery. It has been used to treat choke because it reduces tension in the lower muscles of the esophagus, allowing a blockage to pass. Because it relaxes the muscles of the rectum, Buscopan is sometimes administered to make it easier to perform rectal examinations.

You may be accustomed to your veterinarian reaching for the Banamine when your horse colics, but Buscopan could become another go-to drug of choice for mild cases. Here's what you need to know about this versatile medication.

Class- Antispasmodic

Action/use- Buscopan relaxes smooth muscle cells by inhibiting the parasympathetic nervous system. It is commonly used by equine veterinarians to treat gas (spasmodic) colic, choke and dystocia and to facilitate rectal exams.

Formulations- The only approved formulation of N-butylscopolammonium bromide for horses in the United States is sold as Buscopan, a clear injectable liquid. Although the label specifies intravenous injection, some veterinarians administer the medication intramuscularly.

Storage- Buscopan can be stored at room temperature.

Dose and Duration- The standard dose of Buscopan is .3 mg/kg of body weight, which is 7.5 milliliters for a 1,100 pound horse. Buscopan begins to work immediately. Often a colicky horse is visibly more comfortable 10 minutes after the injection. This action is short-lived, with effects wearing off within a half-hour.

Potential Side Effects- Buscopan can lead to an elevated heart rate, which could mimic the cardiovascular effects of colic or other pain. Heart rate remains elevated for about 30 minutes after administration of the drug.

Courtesy of EQUUS magazine November 2011

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