Ghahramani P, Rowland-Yeo K, Yeo W W, Jackson P R, Ramsay L E
University Department of Medicine and Pharmacology, Royal Hallamshire Hospital, Sheffield, England.
Clin Pharmacol Ther. 1998 Mar;63(3):285-95. doi: 10.1016/S0009-9236(98)90160-6.
Methods for measuring protein binding of drugs generally require direct measurement of the concentration of unbound drug and thus may require a highly sensitive assay. In vivo ultrafiltration has been used to determine protein binding of endogenous substances. We have examined its value for measuring protein binding of drugs because it requires measurement of only the concentration of total drug, not unbound drug, in plasma.
The protein binding of aspirin and its metabolite salicylate was measured in 29 healthy subjects 20 minutes after a single oral dose of 600 mg soluble aspirin, by the new method, in vivo ultrafiltration, as well as by a standard method, in vitro ultracentrifugation.
The data for salicylate were examined systematically to determine the optimal method of determining estimates of protein binding by in vivo ultrafiltration. Estimates of protein binding of salicylate were 81.7% +/- 10.1% (mean +/- SD) by the in vivo method and 81.6% +/- 11.3% by in vitro ultracentrifugation. Bland-Altman analysis of agreement showed that within-individual differences in percentage of protein binding determined by the two methods did not differ significantly from zero (mean difference, 0.07%; 95% confidence interval, -2.33 to +2.46). There was a highly significant correlation between estimates of protein binding by the two methods (r = 0.82; p = 0.001). Protein binding of aspirin was estimated of protein binding by the two methods (r = 0.82; p = 0.001). Protein binding of aspirin was estimated at 58.3% +/- 9.6% by in vivo ultrafiltration and could not be estimated by in vitro ultracentrifugation because the concentration of unbound aspirin in plasma was below the limit of detection for the assay.
In vivo ultrafiltration can be used to measure protein binding of drugs and has potential advantages over conventional methods. A sensitive assay may not be required because the unbound drug need not be measured, measurement in vivo may maintain more physiologic conditions, and it may be useful in measuring protein binding of drugs that are degraded rapidly in vitro.
测量药物蛋白结合率的方法通常需要直接测量游离药物的浓度，因此可能需要高灵敏度的检测方法。体内超滤已被用于测定内源性物质的蛋白结合率。我们研究了其在测量药物蛋白结合率方面的价值，因为它仅需测量血浆中总药物的浓度，而非游离药物的浓度。
采用新方法（体内超滤）以及标准方法（体外超速离心），对29名健康受试者单次口服600mg可溶性阿司匹林20分钟后的阿司匹林及其代谢产物水杨酸的蛋白结合率进行测量。
系统检查了水杨酸的数据，以确定通过体内超滤测定蛋白结合率估计值的最佳方法。通过体内方法测定的水杨酸蛋白结合率估计值为81.7%±10.1%（均值±标准差），通过体外超速离心法测定的为81.6%±11.3%。一致性的布兰德-奥特曼分析表明，两种方法测定的蛋白结合率百分比的个体内差异与零无显著差异（平均差异为0.07%；95%置信区间为-2.33至+2.46）。两种方法测定的蛋白结合率估计值之间存在高度显著的相关性（r = 0.82；p = 0.001）。通过体内超滤测定的阿司匹林蛋白结合率估计为58.3%±9.6%，而通过体外超速离心法无法估计，因为血浆中游离阿司匹林的浓度低于该检测方法的检测限。
体内超滤可用于测量药物的蛋白结合率，与传统方法相比具有潜在优势。由于无需测量游离药物，可能不需要灵敏的检测方法；体内测量可能更能维持生理条件，并且在测量体外快速降解的药物的蛋白结合率方面可能有用。
