Roberts M S
Department of Medicine, University of Queensland, Princess Alexandra Hospital, Buranda, Australia.
J Pharm Sci. 1996 Jun;85(6):655-65. doi: 10.1021/js9500621.
The uptake of solutes into plastic infusion and perfusion tubing has been well documented, but the kinetics of the uptake process is not well-defined. Three mathematical models have been developed to describe the outflow fraction concentration--time profiles for solutes sorbed into the plastic tubing during infusion and perfusions. The models are referred to as model 1, convection--diffusion; model 2, convention-- interfacial resistance--diffusion; ad model 3, convection--interfacial resistance--infinite sink models. In each model, plug flow is assumed and, in order to minimize the number of variables required, solutions are limited to early times when the plastic behaves as an infinite sink. Initial conditions of (i) no solution in the tubing and (ii) a preloading of tubing with drug solution are considered for each of the three models. Two parameters, one being the transit time of solution through tubing (tmin) and the other a measure of the affinity and diffusivity of the solute in the plastic (SN), are sufficient to describe the outflow concentration--time profiles for solutes with sorption into tubing being limited by diffusion in the plastic (model 1). A single parameter, which is the effective interfacial permeability coefficient (H), is sufficient to describe the outflow concentration--time profiles for solutes with sorption into tubing being limited by an aqueous--plastic interfacial barrier (model 3). The three parameters (tmin, SN, and H) are required when uptake into tubing is limited by a combination of diffusion into plastic and an interfacial resistance (model 3). Each model has a characteristic outflow concentration--time profile determined by the relative magnitude of diffusivity of the solute in the plastic to that across the interfacial barrier. The sorption of nitroglycerin and isosorbide dinitrate are adequately described by the convection--diffusion model (model 1 (ii)) whereas the convection--interfacial resistance--diffusion model (model 2 (ii)) is required to describe the sorption of diazepam and chlorpromazine.
溶质在塑料输液管和灌注管中的摄取已有充分记录，但摄取过程的动力学尚未明确界定。已开发出三种数学模型来描述溶质在输液和灌注过程中吸附到塑料管中时流出分数浓度-时间曲线。这些模型分别称为模型1，对流-扩散模型；模型2，对流-界面阻力-扩散模型；以及模型3，对流-界面阻力-无限汇模型。在每个模型中，均假定为活塞流，并且为了尽量减少所需变量的数量，仅在塑料表现为无限汇的早期阶段求解。对于这三种模型中的每一种，均考虑了两种初始条件：（i）管中无溶液；（ii）管中预先装有药物溶液。对于溶质在塑料中的吸附受扩散限制（模型1）的情况，两个参数足以描述溶质的流出浓度-时间曲线，其中一个参数是溶液通过管道的传输时间（tmin），另一个参数是溶质在塑料中的亲和力和扩散系数的量度（SN）。对于溶质在管道中的吸附受水-塑料界面屏障限制（模型3）的情况，单个参数，即有效界面渗透系数（H），足以描述溶质的流出浓度-时间曲线。当溶质在管道中的摄取受扩散到塑料中和界面阻力共同限制时（模型2），则需要这三个参数（tmin、SN和H）。每个模型都有一个特征性的流出浓度-时间曲线，该曲线由溶质在塑料中的扩散系数与跨界面屏障的扩散系数的相对大小决定。硝酸甘油和硝酸异山梨酯的吸附可用对流-扩散模型（模型1（ii））充分描述，而地西泮和氯丙嗪的吸附则需要用对流-界面阻力-扩散模型（模型2（ii））来描述。
