Oral omeprazole is used in the management of equine gastric ulcer syndrome (EGUS). However, its use may have limitations with regard to individual variation in absorption and the impact of dietary management on bioavailability. The objective of this study was to determine whether a novel compounded long-acting injectable omeprazole (LAO-USA) formulation would provide consistent serum omeprazole concentrations and to determine whether it was clinically safe and efficacious in the reduction of EGUS. Twenty-three horses with EGUS described as having evidence of equine squamous gastric disease (ESGD) and/or equine glandular gastric disease (EGGD) received a 5 mg/kg bwt intramuscular injection of LAO-USA once every 7 days for four doses. Gastroscopy was performed prior to the study and at Days 14 and 28. Pharmacokinetic analysis was performed to determine omeprazole concentrations over 7 days. Safety was measured by monitoring injection site reactions daily and bloodwork screening prior to and following the study. Of the horses with ESGD, 78% had improvement by Day 14 (p = 0.0035), with no further improvement from Day 14 to 28 (p > 0.99). ESGD grades from Day 0 to 28 decreased significantly (95% CI −1.92 to −0.91 grades) (p = 0.0002). Out of the horses (6/23) that had glandular lesions, 5/6 healed over time; however, this was not a significant change (p = 0.75). Injection reactions included oedema, heat and pain at the injection site. Considering the total number of injections across the whole study, 23% of horses experienced an injection site reaction. The number of injection site reactions increased following each dose (8%, 13%, 22% and 48%, respectively). The formulation did not appear to have adverse systemic effects. Serum omeprazole mean C_max was 46.2 ng/ml (±17.4 ng/ml), and these concentrations maintained at approximately 9.6 ng/ml (±4.6 ng/ml) for 7 days following dosing. This formulation is compounded and has not completed FDA investigation, which may increase formulation variability as it is produced or stored. The lack of control groups and potential bias in lesion grading are additional recognised limitations. The results of this study provide preliminary safety and efficacy data with regard to a novel LAO-USA formulation. Future study is warranted to describe safety and efficacy for both ESGD and EGGD and would support further FDA investigation.

中文翻译：

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新型长效肌注奥美拉唑对胃溃疡表现马的临床疗效、安全性和药代动力学

口服奥美拉唑用于治疗马胃溃疡综合征 (EGUS)。然而，在吸收的个体差异和饮食管理对生物利用度的影响方面，其使用可能存在局限性。本研究的目的是确定一种新型复合长效注射奥美拉唑 (LAO-USA) 制剂是否能提供一致的血清奥美拉唑浓度，并确定其在减少 EGUS 方面是否具有临床安全性和有效性。23 匹患有 EGUS 的马被描述为有马鳞状胃病 (ESGD) 和/或马腺性胃病 (EGGD) 的证据，每 7 天接受一次 5 mg/kg bwt 的 LAO-USA 肌肉注射，共四剂。在研究前和第 14 天和第 28 天进行胃镜检查。进行药代动力学分析以确定奥美拉唑在 7 天内的浓度。通过每天监测注射部位反应和研究前后的血液检查来测量安全性。在患有 ESGD 的马中，78% 的马在第 14 天时有所改善（p  =  0.0035)，从第 14 天到第 28 天没有进一步改善 ( p  > 0.99)。第 0 天到第 28 天的 ESGD 等级显着下降（95% CI -1.92 到 -0.91 等级）（p  = 0.0002）。在有腺体病变的马（6/23）中，5/6 随着时间的推移愈合；然而，这并不是一个显着的变化（p  = 0.75）。注射反应包括注射部位的水肿、发热和疼痛。考虑到整个研究中的注射总数，23% 的马经历了注射部位反应。每次给药后注射部位反应的数量增加（分别为 8%、13%、22% 和 48%）。该制剂似乎没有不良的全身作用。血清奥美拉唑平均C _max为 46.2 ng/ml (±17.4 ng/ml)，并且这些浓度在给药后 7 天内维持在大约 9.6 ng/ml (±4.6 ng/ml)。该配方是复合配方，尚未完成 FDA 调查，这可能会在生产或储存时增加配方的可变性。缺乏对照组和病变分级的潜在偏差是另外公认的限制。这项研究的结果提供了关于一种新的 LAO-USA 制剂的初步安全性和有效性数据。未来的研究有必要描述 ESGD 和 EGGD 的安全性和有效性，并将支持 FDA 的进一步调查。