Murchie T A, Macpherson M L, LeBlanc M M, Luznar S, Vickroy T W
Western University of Health Sciences, College of Veterinary Medicine, Pomona, California 91766, USA.
Equine Vet J. 2006 Nov;38(6):520-5. doi: 10.2746/042516406x156136.
Most current treatments for placentitis in mares are empirical with few control studies to evaluate their effectiveness.
To monitor drug concentrations in allantoic fluid of pregnant pony mares using in vivo microdialysis and establish if this method would be useful for determining allantoic concentrations of drugs in normal mares and those with placentitis.
Five late gestational pony mares had microdialysis probes inserted into the allantoic fluid using transabdominal ultrasound-guided allantocentesis. Single injections of penicillin G (22,000 u/kg), gentamicin (6.6 mg/kg bwt) and flunixin meglumine (1 mg/kg bwt) were administered i.v. and dialysate samples collected continuously for 24 h. In a separate study, drug concentrations were monitored in allantoic fluid of 2 mares with experimental placentitis induced by intracervical inoculation with Streptococcus equi ssp. zooepidemicus. Drug concentrations were measured by high performance liquid chromatography (penicillin G, flunixin meglumine) or enzyme-linked immunosorbent assay (gentamicin).
Penicillin G and gentamicin achieved average peak concentrations of 9.8+/-2.2 and 8.5+/-3.1 microg/ml, respectively, in allantoic fluid of noninfected mares. Pharmacokinetic comparisons indicate that penicillin G persists much longer in allantoic fluid than blood, whereas gentamicin exhibited similar profiles in the 2 compartments. Flunixin meglumine was not detected in allantoic fluid. In infected mares, penicillin G achieved a similar peak concentration in allantoic fluid (11.2 microg/ml) whereas peak gentamicin concentration (3.9 microg/ml) appeared to be reduced relative to drug concentrations in noninfected mares.
Microdialysis is a useful technique for continuous in vivo monitoring of drugs in equine allantoic fluid. Our results indicate that penicillin G and gentamicin undergo effective placental transfer in pregnant mares and in 2 mares that transplacental drug transfer may be altered selectively if active placental infection is present.
Further studies are needed to evaluate the feasibility of using increased dose intervals for penicillin G and an increased dose rate of gentamicin to effectively combat placental infections in mares.
目前母马胎盘炎的大多数治疗方法都是经验性的，很少有对照研究来评估其有效性。
使用体内微透析监测妊娠母马尿囊液中的药物浓度，并确定该方法是否有助于测定正常母马和患有胎盘炎母马的尿囊液中药物浓度。
对5匹妊娠晚期的母马，经腹超声引导下进行尿囊穿刺，将微透析探针插入尿囊液中。静脉注射青霉素G（22,000 u/kg）、庆大霉素（6.6 mg/kg体重）和氟尼辛葡甲胺（1 mg/kg体重）单次剂量，连续收集24小时的透析液样本。在另一项研究中，对2匹经子宫颈接种马链球菌兽疫亚种诱导实验性胎盘炎的母马，监测其尿囊液中的药物浓度。通过高效液相色谱法（青霉素G、氟尼辛葡甲胺）或酶联免疫吸附测定法（庆大霉素）测量药物浓度。
在未感染母马的尿囊液中，青霉素G和庆大霉素的平均峰值浓度分别为9.8±2.2和8.5±3.1μg/ml。药代动力学比较表明，青霉素G在尿囊液中的持续时间比在血液中长得多，而庆大霉素在两个腔室中的分布情况相似。在尿囊液中未检测到氟尼辛葡甲胺。在感染母马中，青霉素G在尿囊液中达到了相似的峰值浓度（11.2μg/ml），而庆大霉素的峰值浓度（3.9μg/ml）相对于未感染母马的药物浓度似乎有所降低。
微透析是一种用于连续体内监测马尿囊液中药物的有用技术。我们的结果表明，青霉素G和庆大霉素在妊娠母马中能有效进行胎盘转运，并且在2匹母马中，如果存在活动性胎盘感染，经胎盘药物转运可能会有选择性地改变。
需要进一步研究评估增加青霉素G的给药间隔和提高庆大霉素的给药速率以有效对抗母马胎盘感染的可行性。
