INJECTABLE ULCER DRUG MAY SOON BE AVAILABLE

A long-acting, injectable form of omeprazole may be available for horses soon, according to an Australian researcher who recently completed an efficacy study of the drug.

First developed as a human medicine, omeprazole is used to treat and prevent gastric ulcers in horses. The medication is currently available only in an oral paste formulation that must be administered daily. The new omeprazole formulation is injected intramuscularly every seven days. In addition to less frequent administration, the injectable form of the drug offers other benefits, says Ben Sykes, BVMS, PhD, of the University of Queensland.

“The use of an intramuscular formulation bypasses the problems observed in some horses with very low absorption of omeprazole, especially in horses consuming free-choice hay diets---this would be a key advantage,” says Sykes (see “Effects of Diet on Ulcer Treatment Studied,” Medical Front,

EQUUS 472). “But we also saw higher healing rates in a shorter period of time than previously reported with the oral formulations.”

The study was conducted in two phases. For the first half, Sykes and fellow researchers monitored the stomach pH levels of six racing Thoroughbreds for seven days after an omeprazole injection. On the pH scale, a score of 7 is considered neutral, and the lower the score the more acidic a substance.

The data showed that during the first four days after omeprazole injection all of the horses had a gastric pH of ≥ 4 at least 66 percent of the time, and four of the six exceeded that level for seven days. That 66 percent threshold is considered a significant indicator of gastric healing in people with gastric reflux, explains Sykes, adding that previous research showed that, on average, horses had a gastric pH of ≥ 4 for as little as 30 to 40 percent of the time by the fifth day after administration of oral omeprazole.

For the second half of the study, 26 Thoroughbreds with confirmed gastric ulcers were given two omeprazole injections, one week a w troscope and scored before treatment began and again at the end of the two-week study period. Improvement, by at least one grade, was seen in every horse during that period.

In fact, the ulcers were completely healed in all of the horses who had squamous lesions (found in the top portion of the stomach) and in 9 of 12 horses with glandular lesions (found at the bottom portion). By comparison, healing rates among horses given only oral omeprazole range from approximately 25 percent for glandular lesions and 70 to 85 percent for squamous lesions, after 28 to 35 days of daily treatment.

“The results of this study are particularly promising as, to date, the reported response rates for equine glandular gastric disease (EGGD) have been frustratingly poor,” says Sykes. “The idea of being able to reliably induce acid suppression, regardless of diet, and to potentially treat horses more effectively and in a shorter time is very exciting.” He adds that “the formulation is currently in the process of commercialization and it is anticipated that it will be available in several key markets mid- to late 2017.”

Squamous lesions are found in the top portion of the horse’s stomach, while glandular lesions affect the bottom portion.

Reference: “Preliminary investigations into a novel, long-acting, injectable, intramuscular formulation of omeprazole in the horse,” Equine Veterinary Journal, April 2017

problem is more prevalent in particular breeds, such as Icelandic Horses.

The Czech study focused on Old Grey Kladruber horses, a native warmblood breed, at the National Stud in Kladruby and 10 private breeding facilities. The same person visually inspected the horses over a period of 13 years, from 1996 to 2009, scoring the severity of any signs of IBH at each observation. A total of 1,209 observations were entered in a database, along with information about each horse, including location, age and pedigree. Thereafter, the data were analyzed.

In statistics, the degree of a trait’s heritability is expressed on a 0 to 1 scale, with 0 meaning that none of the variability of the trait among individuals is the result of genetics and 1 meaning that genes are responsible for all the variability. The Czech researchers found the heritability of sweet itch susceptibility among the study horses ranged from 0.305 to 0.626, depending on the factors considered in the calculations. These numbers, the researchers say, indicate the heritability of sweet itch is “medium to high, so there is a possibility to reduce the prevalence of IBH by selection.”

A total of 1,209 observations were entered in a database, along with information about each horse’s location, age and pedigree.

Reference: “Genetic parameters of insect bite hypersensitivity in the Old Grey Kladruber horse,” Journal of Animal Science, January 2017