摘要
脂肪乳因安全性高、适用范围广和起效时间短,在药物中毒解救领域具有广阔的应用前景。本文从部分临床病例报告出发,分析了脂肪乳在局麻类、抗心律失常类、精神类和有机磷酸酯类等多种药物中毒解救中的效果及脂肪乳可能带来的不良反应。同时对脂肪乳的解毒机制:如脂质池理论、机体代谢增强理论和强心作用等,进行了充分阐释。最后对脂肪乳疗法存在的问题提出了可能的解决方案,以期能加深对脂肪乳解毒疗法的了解,促进其在药物中毒临床解救中的合理应用。
药物中毒通常指体内药物浓度高出其最低中毒浓度时所导致的一系列症状,严重时甚至致人死亡。近年来,药物中毒事件发生率不断增加,对公共医疗系统造成极大负
非特异性解毒剂是近年来兴起的一类基于非特异性相互作用(疏水作用、氢键、静电作用等)降低体内有效药物浓度的解毒策略。由于其独自使用时解毒效果有限、静脉注射时会激活补体系统导致过敏样反应、制备过程复杂难以进行有经济效应的大规模生产,非特异性解毒剂多处于临床前研究阶段。但是非特异性解毒剂能迅速捕获多种药物分子,缓解中毒症状,是一种即时的、通用的解毒手段。这种即时性能很大程度改善患者愈后效果,通用性则于急诊医生在解救中毒相关信息不明的患者时具有重大价值。总的来说,非特异性解毒剂极具应用前景,能满足临床对于迅速缓解患者中毒症状、提高患者存活率和改善患者愈后效果的迫切需
脂肪乳(Intralipi
1998年Weinberg
脂肪乳是一种以卵磷脂为乳化剂,油相以小液滴的形式分散于水相(注射用水)中所形成的水包油型乳剂,常加入等渗调节剂甘油、pH调节剂氢氧化钠、助乳化剂油酸钠、抗氧化剂α生育酚等辅料。根据脂肪乳中油相的种类可以将其分为3
脂肪乳的粒径在300 ~ 400 nm之间、颗粒表面显负电、稳定性高(在4 ℃条件下可保存至少两年,无明显沉降、聚集等现象)。脂肪乳进入血液之后代谢途径与天然乳糜微粒相
Weinberg
抗心律失常药是一类临床上常用的用于防治心动过速和心率不齐的药物,但使用不当时反而会导致一系列中毒症状,如心动过缓、QT间期延长等,严重时危及患者生命。Cave
有相当多的临床病例显示脂肪乳在抗心律失常药物中毒解救中依然有效(
在精神类药物中,阿米替林、安非他酮、文拉法辛等抗抑郁药的中毒最为常见。动物实验显示,静脉给予脂肪乳,可以改善阿米替林过量导致的血流动力学紊
有机磷酸酯类属于难逆性抗胆碱酯酶药,过量时会产生中枢神经系统中毒症状,常用的治疗方案为血液灌流、抗胆碱能药以及胆碱酯酶复活剂联合治疗。为了提升治疗效果,有研究将静脉给予脂肪乳,并入上述常规治疗方案中,取得了良好的效
上述研究表明,脂肪乳可以用于多种类型药物的中毒解救。但应注意到,Litonius
脂质池理论认为:脂肪乳进入血液之后,油性乳滴对脂溶性药物的高亲和力将驱动药物分子从血液分配至脂肪乳的脂质池,降低血液中游离药物浓度;同时分配至脂肪乳中的药物将随脂肪乳共同分布至肝脏、肌肉和脂肪等组织,药物的体内分布得以改变。在这两个效果的影响下,能与靶点结合的药物分子大大减少,药物的疗效/毒性也因此大大降低,从而达到解毒效果。该理论最初是由Weinberg
(1) |
式中,B是脂肪乳对于该药物的实际装载量,是脂肪乳对于该药物最大的分配效率,Lip是脂肪乳浓度,F是未被装载的药物量,是脂肪乳与药物间的解离常数。为了进一步验证脂质池理论,French
之后研究人员分析了脂肪乳对于药物代谢动力学和组织分布的影响。Shi
脂质池理论可以很好地解释脂肪乳对于脂溶性药物解毒的广谱性。但脂质池理论难以解释脂肪乳对于一些脂溶性较弱的药物,如阿替洛尔、美托洛尔和丙胺卡因等,也具有较好的解毒作用。同时,对于一些脂溶性较强药物,脂肪乳的疗效不如预期。这表明脂肪乳可能还存在其他的解毒机制。现有提出的脂肪乳解毒机制还包括:促代谢和正面促进心血管功能。
脂肪酸作为一种重要的代谢底物,可在细胞质基质和线粒体中,通过β-氧化分解为二氧化碳和水,同时释放大量能量。这提示脂肪乳中的大量脂肪酸在肝和肌肉中被代谢后,释放的大量能量可调节一些药物中毒所导致的代谢障碍,因此脂肪乳对于一些影响基础代谢的药物也具有一定的解毒作
脂肪乳的制备工艺简单成熟,是一种非常经济的治疗剂,能为绝大多数患者所承受;其次,脂肪乳的使用至今已有40余年,其安全性有着强有力的保障;同时脂肪乳的脂质池使其可以作为一种广谱解毒剂用于多种类型药物解毒;且随着对脂肪乳的解毒机制研究越来越深入,特别是对于脂质池理论的充分理解,加上大量成功或者失败案例的报道,脂肪乳作为解毒剂的应用范围也逐渐清晰。脂肪乳所具有的这些优势让其在解毒剂方向上具有非常良好的临床应用前景,因此也是目前唯一被推荐用于临床的非特异性解毒剂。
但也应注意到脂肪乳作为解毒剂使用还存在许多亟待解决的问题:(1)脂质池的存在降低了游离血药浓度,改变了药物分布,导致药物更多被分配至肝脏和肌肉组织中从而发挥解毒效果。这种组织分布的改变对于某些类型的药物中毒解救是有利的,但是对于靶点在肝脏或者肌肉组织的药物来说,脂肪乳的使用可能会加剧药物对肝脏或者肌肉的靶向性,甚至进一步加深中毒症状;(2)相似地,脂肪乳的代谢增强作用和心血管效应使得脂肪乳可能不适合于促代谢以及强心的药物;(3)由于某些药物本身性质的原因,如一些非线性消除药物,其药效与剂量之间的关系存在一个转折点,在高于此剂量时,剂量的改变对于药效没有明确的影响;只有低于此剂量,药效才会随着剂量的降低而迅速减弱。这使得在解救该类药物中毒时至少需要将体内剂量降低至阈值之下,因此在使用脂肪乳解救时所需的剂量往往会大幅增加。即使脂肪乳的安全性很高,依然可能导致一系列不良反应的出现,这也限制了脂肪乳在解毒剂方面的使用;(4)脂肪乳主要通过改变药物代谢动力学和药物组织分布在药物中毒解救中发挥解毒作用,同理,脂肪乳也可以改变正常剂量下药物的代谢动力学和组织分布从而减弱药物疗效。那么,对于同时使用其他药物(非中毒药物)的药物中毒患者,脂肪乳的使用应更为小心,避免导致其他药物的浓度降至最低有效浓度之下。另一方面也提示对于同时使用脂肪乳和治疗药物的患者,药物剂量应该适当增加,或者脂肪乳、药物的服用时间应仔细规划,避免脂肪乳对于药物疗效的影响;(5)目前对脂肪乳解毒的研究主要是通过单一动物实验或者个别病例报道去说明脂肪乳的有效性,而对脂质池所赋予的广谱性研究甚少,特别是在定量描述其广谱性方面几乎没有相关研究,这些信息对于明确脂肪乳作为解毒剂使用的适用范围,进而帮助临床医生迅速判断脂肪乳是否适用于某种药物中毒,争取抢救的黄金时间是不可或缺的。
由于脂肪乳会捕获血液中游离药物,从而加速大部分药物代谢,最终缓解患者中毒症状。因此,本课题组正在通过定量表征脂肪乳对药物的捕获能力,如乳滴内能容纳的最大药物分子数以及药物进入脂肪乳油相内的速率,来预测脂肪乳对过量药物的代谢动力学影响,从而预评估脂肪乳解毒效果。相关研究结果表明,定量化的脂肪乳捕获能力与药物代谢动力学受脂肪乳影响的程度之间存在显著的相关性,据此建立的定量关系可以精准预测使用脂肪乳后,药物代谢动力学受影响的程度。而根据脂质池理论-药物lgP建立的定量关系则不能精准预测药物代谢动力学的变化。这是因为脂肪乳捕获能力同时反映了药物在水和脂肪乳油相中的平衡,以及药物从水相进入油相的速率,更加精确地描述了脂肪乳捕获药物这一过程;而药物lgP仅仅反映了药物在水和正辛醇中的分配平衡。该研究提出的脂肪乳捕获能力是对脂质池理论的修正和完善,据此可以更好地去判断脂肪乳解毒疗法在临床上的应用范围,挽救更多患者的生命。
总之,脂肪乳被用于解毒剂的研究已经取得了较大的进展,但仍有大量问题亟待解决,相关研究人员应继续深耕细作,解决脂肪乳作为解毒剂使用的相关问题,从而加快推动脂肪乳在临床上的合理应用。
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