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®（图拉霉素）在健康成年马中的药代动力学和肺部分布。

这项研究的目的是确定对六只成年马进行肌肉内（IM），皮下（SC）和缓慢静脉内（IV）给药后，图拉霉素（Draxxin®；一次； 2.5 mg / kg）的药代动力学和耐受性。使用了三相设计和4周的清洗期。通过超高效液相色谱串联质谱法测定血液和支气管肺泡灌洗液（BAL）样品中的药物浓度，并使用非区室分析法计算药代动力学参数。在SC和IM给药后，所有马匹均出现出汗，不适和卧卧期。由于SC给药后体征更严重，该途径仅用于3/6匹马。在所有的马中，静脉注射图拉霉素的耐受性都很好。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。IV，IM和SC的平均半衰期分别为59.8小时，54.8小时和57.9小时。静脉内给药后，平均清除率为3.25 ml / kg / min，平均分布体积为16.8 L / kg。遵循所有路线，在血浆和BAL样品中可检测药物120小时。但是，不良影响可能会阻止IM的使用，因此不建议使用SC。图拉霉素可能是一种实用且价格合理的抗微生物剂，可用于成年马患者。但是，不良影响可能会阻止IM的使用，因此不建议使用SC。图拉霉素可能是一种实用且价格合理的抗微生物剂，可用于成年马患者。但是，不良影响可能会阻止IM的使用，因此不建议使用SC。图拉霉素可能是一种实用且价格合理的抗微生物剂，可用于成年马患者。