The objective of this study was to determine the pharmacokinetics and tolerability of tulathromycin (Draxxin^®; 2.5 mg/kg once) after intramuscular (IM), subcutaneous (SC), and slow intravenous (IV) administration to six adult horses. A three-phase design and 4-week washout period were used. Drug concentrations in blood and bronchoalveolar lavage (BAL) samples were determined by ultra-performance liquid chromatography tandem mass spectrometry and pharmacokinetic parameters calculated using noncompartmental analysis. Following SC and IM administration, all horses exhibited sweating, discomfort, and periods of recumbency. As signs were more severe after SC administration this route was only used in 3/6 horses. Intravenous administration of tulathromycin was well tolerated in all horses. Mean bioavailability was 99.4% IM and 115% SC. Mean maximum plasma concentration was 645 ng/ml IM and 373 ng/ml SC. Mean half-life was 59.8 h, 54.8 h, and 57.9 h for IV, IM, and SC administration, respectively. Mean clearance was 3.25 ml/kg/min, and mean volume of distribution was 16.8 L/kg following IV administration. Drug was detectable in plasma and BAL samples for 120 h following all routes; however, adverse effects may prevent IM use and SC use is not recommended. Tulathromycin may be a practical and affordable antimicrobial for use in adult equine patients.

中文翻译：

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Draxxin®（妥拉霉素）在健康成年马中的药代动力学和肺部分布

本研究的目的是确定妥拉霉素 (Draxxin ^®; 2.5 mg/kg 一次）在肌肉内 (IM)、皮下 (SC) 和缓慢静脉内 (IV) 给药后对六匹成年马进行。使用了三阶段设计和 4 周的冲洗期。血液和支气管肺泡灌洗 (BAL) 样品中的药物浓度通过超高效液相色谱串联质谱法和使用非房室分析计算的药代动力学参数确定。在 SC 和 IM 给药后，所有马都表现出出汗、不适和卧床。由于 SC 给药后体征更加严重，该途径仅用于 3/6 匹马。所有马都对静脉注射托拉霉素有良好的耐受性。平均生物利用度为 99.4% IM 和 115% SC。平均最大血浆浓度为 645 ng/ml IM 和 373 ng/ml SC。对于 IV、IM、和 SC 管理，分别。IV 给药后平均清除率为 3.25 ml/kg/min，平均分布容积为 16.8 L/kg。在所有途径后 120 小时内，可在血浆和 BAL 样品中检测到药物；然而，副作用可能会妨碍 IM 的使用，不推荐 SC 使用。妥拉霉素可能是一种实用且价格合理的抗菌剂，可用于成年马患者。