氟苯尼考在猪体内对胸膜肺炎放线杆菌的生理药动-药效学研究

Florfenicol (FF) is widely used for the control of porcine contagious pleuropneumonia in China. The use of FF in practice is based on the the minimal inhibitory concentration, which may lead to treatment failure, bacterial resistance, and violative residues in edible tissues, because the dosing regimen is developed without considering the affect of the in vivo disposition of antimicrobial agents on its pharmacodynamic. Physiologically based pharmacokinetic-pharmacodynamic (PBPK-PD) model has been proved to be a powerful tool to simultaneously simulate the changes in the antibiosis effect and drugs level in target compartment over time, and can be used for the development of dosing regimen of antimicrobial agents. In the current study, the predictive PBPK model for FF in pig will be developed according to a step-by-step procedure as follow: 1. model parameters will be collected from literatures and determined in in-vitro and in-vivo studies, 2. resonable hypotheses on the dispositon of FF in pig will be put forward based on existing research, and the model structure and equations will be constructed, 3. the predictive model will be developed after debugged and validated. Then, the validated PBPK model and an in-vitro dynamic model will be used to creat concentration-time curve and dynamic time-kill curve, respectively. Finally, the PBPK-PD model for FF in pig will be developed. The use of the validated PBPK-PD model in practice can improve the cure rate of porcine contagious pleuropneumonia and reduce the antimicrobial resistance of streptococcus against FF.

氟苯尼考(FF)是治疗猪传染性胸膜肺炎的首选药。在兽医临床上，FF的使用主要依据最小抑菌浓度(MIC)。但是以MIC制订给药方案忽视了FF体内处置对药效的影响，往往导致治疗失败、耐药性产生等诸多问题。而现有的药动-药效学研究以血液或组织笼液代替感染部位预测FF药效，准确性有待提高。生理药动-药效学(PBPK-PD)模型能模拟感染部位药物浓度和药效的经时变化，可用于指导FF的合理使用。本课题以FF和胸膜肺炎放线杆菌为研究对象，按照"收集参数→构建模型→模型拟合→模型验证"的思路建立预测性的生理药动学模型，再根据该模型的预测结果，采用体外动力学模型研究感染部位FF浓度与药效的关系，最终建立FF的PBPK-PD模型。课题的完成有助于阐明感染部位FF浓度、药效和时间之间的关系，为FF制订科学的用药方案提供理论依据。研究成果的应用有助于提高FF治疗猪传染性胸膜肺炎的效果，减少不合理使用导致的耐药性。

氟苯尼考抗菌效果好，毒副作用小，是治疗猪传染性胸膜肺炎的首选药。兽医临床上，制定氟苯尼考给药方案的依据是最小抑菌浓度和血药浓度-时间数据。然而，血药浓度与抗菌效果并无直接联系，由此制定给药方案尚存在争议。为避免不合理用药导致的治疗失败和耐药性，有必要重新评估、设计氟苯尼考的给药方案。本研究建立了定量分析猪体液中氟苯尼考含量的高效液相色谱法，结合微透析技术测定了药物作用部位——肺组织间液中氟苯尼考的浓度-时间数据，并建立了预测性的生理药动学模型。依据模型预测结果和最新的药敏试验数据，课题组重新评估、推荐了氟苯尼考的给药方案。.可靠的生物样品分析方法是开展药动学研究的基础。课题组建立了猪血浆、尿液和肺微透析液中氟苯尼考的定量分析方法。方法的特异性、线性、范围、准确性、精确性和灵敏性均满足后续研究的需要。方法以经典的薄层色谱法净化样品提取物，净化效果好，绿色，检测成本低廉，为解决复杂样品基质中痕量化合物的分离纯化这一技术瓶颈提供了新思路。.对于绝大多数细菌性呼吸道感染，肺组织间液中抗菌药物浓度是评价抗菌效果的金标准。课题组采用微透析技术测定了肌注不同剂量的氟苯尼考后猪肺组织间液中的该药物的浓度-时间数据。非房室分析的结果表明，氟苯尼考在肺组织间液中具有分布迅速但消除缓慢的特点，不同剂量间Tmax，t1/2，λz无显著差异。此研究成果已发表于Journal of Veterinary Pharmacology and Therapeutics杂志。.基于上述研究，课题组按照“提出假设→构建模型结构→编写质量平衡方程→收集、拟合模型参数→灵敏性分析→模型验证”的思路建立了预测性的生理药动学模型。经与实测数据比对，模型能准确预测不同给药方案下肺组织间液、血液、肌肉、肝脏、肾脏和肺脏中氟苯尼考的动态变化，但对注射部位的预测存在偏差。模型在兽医临床上的应用将为评估、设计氟苯尼考的给药方案提供更加科学的依据。此研究成果已投稿于Journal of Veterinary Pharmacology and Therapeutics杂志，并修回（major revision）。