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Gastric ulcers are common in horses. The purpose of this study was to test the effect of a commercially available supplement, SmartGut® Ultra pellets (SmGU) on gastric ulcer scores and gastric juice pH after omeprazole treatment in stall-confined horses. Eight Thoroughbred horses were studied in a 2-period, 2-treatment crossover design, where the SmGU (40 g, twice daily) was mixed in grain feed. Horses were stall-confined and treated with the supplement or control for 6 weeks, consisting of 2 weeks (Days 1-14) omeprazole treatment, 2 weeks (Days 14-28) following discontinuation of omeprazole treatment, one week (Days 28-35) alternating feed deprivation to induce or worsen existing ulcers and a one week (Days 35-42) recovery period. Gastroscopy was performed and gastric juice pH measured on Days 0, 14, 28, 35 and 42. Gastric ulcer lesion number (NGN) and severity (NGS) scores were assigned to each horse by an investigator (F.M.A.) masked to treatment. On Day 0 before treatment, mean NGN and NGS scores and gastric juice pH were not different (P>0.05) between treatment groups. By Day 14, mean NGN and NGS scores decreased (P<0.05) in both treatment groups. By Days 28 and 35, mean NGN score significantly increased in the untreated control horses but not the SmGU-treated horses. By Day 42, mean NGN and NGS scores were not different in either group and were significantly lower than Day 0. Mean gastric juice pH was higher in both groups on Day 14 as a result of omeprazole treatment when compared with other days. SmartGut® Ultra supplement added to the feed prevented the worsening of gastric ulcer number 2 weeks after omeprazole treatment, without altering the gastric juice pH. Supplementation with SmGU might aid in protection of the nonglandular stomach from recurrence of ulcers after omeprazole treatment in stall-confined horses undergoing intermittent feeding. [ABSTRACT FROM AUTHOR]

Linardi, R. L., Stokes, A. M., Andrews, F. M. The effect of P-Glycoprotein on methadone hydrochloride flux in equine intestinal mucosa. J. vet. Pharmacol. Therap. 36, 43-50. Methadone is an effective analgesic opioid that may have a place for the treatment of pain in horses. However, its absorption seems to be impaired by the presence of a transmembrane protein, P-glycoprotein, present in different tissues including the small intestine in other species. This study aims to determine the effect of the P-glycoprotein on methadone flux in the equine intestinal mucosa, as an indicator of in vivo drug absorption. Jejunum tissues from five horses were placed into the Ussing chambers and exposed to methadone solution in the presence or absence of Rhodamine 123 or verapamil. Electrical measurements demonstrated tissue viability for 120 min, and the flux of methadone across the jejunal membrane (mucosal to submucosal direction) was calculated based on the relative drug concentration measured by ELISA. The flux of methadone was significantly higher only in the presence of verapamil. P-glycoprotein was immunolocalized in the apical membrane of the jejunal epithelial cells (enterocytes), mainly located in the tip of the villi compared to cells of the crypts. P-glycoprotein is present in the equine jejunum and may possibly mediate the intestinal transport of methadone. This study suggests that P-glycoprotein may play a role in the poor intestinal absorption of methadone in vivo. [ABSTRACT FROM AUTHOR]

Gastric ulcers are common in horses and treatment of horses that cannot be administered oral medication can be problematic. To evaluate the efficacy of esomeprazole sodium administered intravenously on gastric juice pH and gastric ulcer scores in horses. Twelve adult female Quarter Horses. Esomeprazole sodium (0.5 mg/kg IV) was administered once daily to 8 horses (treatment group) and saline (5 mL IV) was administered to 4 horses (control group) for 13 consecutive days. Gastroscopy was performed and gastric juice pH and gastric ulcer score were recorded before and 1 hour after the administration of esomeprazole sodium or saline on days 1 and 5, then on day 14, 23 hours after the 13th daily dose of esomeprazole sodium or saline. When compared with values before treatment, gastric juice pH was higher in esomeprazole sodium-treated horses after treatment (4.25 ± 2.39 versus 6.43 ± 1.18; P= .002). Also, gastric juice pH was higher ( P= .001) in esomeprazole sodium-treated horses compared with saline-treated control horses on day 5 and on day 14 values. Gastric ulcers were seen in 5/12 (43%) horses in the study. Esomeprazole sodium shows promise for treatment of gastric ulcers in horses with signs of dysphagia, gastric reflux, or other conditions that restrict oral intake of the current Federal Drug Administration-approved omeprazole paste. [ABSTRACT FROM AUTHOR]

In this article, the author comments on a case study on the ante mortem diagnosis of necrotising emphysematous oesophagitis and gastritis in a horse by D. Whelchel and colleagues published in the current issue. The author says that this report confirms that radiography, ultrasonography and computed tomography are likely to provide an ante mortem diagnosis for emphysematous oesophagitis and gastritis which serious conditions in horses and other species.

Endotoxaemia is one of the most severe and ubiquitous disease processes in horses; and delayed gastric emptying is one of the most clinically significant manifestations of endotoxaemia. Current information suggests that oxidative damage plays a key role in the systemic effects induced by endotoxin and this raises the possibility that antioxidants, such as dimethyl sulfoxide (DMSO), might have a protective effect. No study has yet evaluated the efficacy of DMSO in ameliorating delayed gastric emptying caused by endotoxaemia in horses. We hypothesized that DMSO would ameliorate delayed gastric emptying caused by intravenous lipopolysaccharide (LPS) administration. Horses were randomly assigned to one of 4 groups; of 6 horses each: Normosol (Abbott Laboratories, Abbott Park, Illinois, USA) + LPS (0.2µg/kg bwt, i.v.); DMSO (1g/kg bwt, i.v.) + Saline; High-dose DMSO (1g/kg bwt, i.v.) + LPS; Low-dose DMSO (20 mg/kg bwt, i.v.) + LPS. All horses in all groups received acetaminophen (20 mg/kg reconstituted in one liter of warm tap water) by nasogastric intubation. Data for acetaminophen concentrations in the blood as a measure of gastric emptying were examined for the effect of treatment using a repeated-measures mixed-model ANOVA. A value of P < 0.05 was considered significant. Delayed gastric emptying occurred in all horses receiving LPS, as indicated by the lower concentrations of acetaminophen in these groups along the study period. DMSO did not ameliorate the effect of LPS on gastric emptying. Low-dose DMSO actually exacerbated the LPS-induced delay in gastric emptying. In this study, DMSO did not have any protective effect against LPS-induced delayed gastric emptying in horses. [ABSTRACT FROM AUTHOR]