The influence of volume ratio of ultrafiltrate of sample on the analysis of non-protein binding drugs in human plasma

Abstract

In human plasma, the total concentration of non-protein binding (NPB) drugs is equal to the free drug concentration because NPB drugs do not or hardly bind to plasma proteins. Thus, centrifuge ultrafiltration (CF-UF) has been used in the determination of the concentration of NPB drugs in human plasma. However, with only a common centrifugation, the recovery and the reproducibility were not as excellent as expected. In addition, we discovered that the values of the volume ratio of ultrafiltrate to sample solution (Vu/Vs) were different and could not be well controlled, which may affect the determination of the drug concentration. The problem also affected the determination of other NBP drugs. In the present work, we used biapenem as a representative drug to study the effect of Vu/Vs on the analysis of NPB drugs concentration in human plasma. The results showed that a Vu/Vs value of less than 0.4 had no effect on the analysis of free drug concentration, while a Vu/Vs value of more than 0.4 was associated with increased recovery rate and overestimation of drug concentration. Therefore, to maintain a Vu/Vs value of less than 0.4 and even at a constant value is the key to accurately determine the concentration of NPB drugs in plasma. Fortunately, with an HFCF-UF device, the Vu/Vs could be well controlled and kept at 0.08 in this study. The recovery rates were almost 100% and the analysis precision was greatly improved. In pharmacokinetics studies, this method was successfully employed to determine the concentration of biapenem with excellent accuracy and reproducibility. HFCF-UF may become a feasible platform for the determination of NPB drugs.

Pretreatment of plasma samples by a novel hollow fiber centrifugal ultrafiltration technique for the determination of plasma protein binding of three coumarins using acetone as protein binding releasing agent

“…In our previous work, HFCF-UF has been introduced to determine the unbound drug concentration and excellent results have been achieved [21][22][23]42]. This method introduces hollow fiber membrane as the media to intercept biological macromolecular matrix, so that the small molecule drugs can pass through the hollow fiber membrane freely.…”

“…Meanwhile, the volume ratio of ultrafiltrate to sample solution was small, leading to a hardly affected drug-protein binding equilibrium with perfect recovery (around 100%) and precision [21,22].…”

“…Hollow fiber centrifugal ultrafiltration (HFCF-UF), a simple device composed of a slim glass tube and a U-shaped hollow fiber, has been introduced for the separation of unbound drug fraction from plasma sample [21][22][23]. Since the direction of centrifugal force is completely parallel to the hollow fiber membrane, concentration polarization is avoided and the small molecules can pass through the membrane freely [24,25].…”

“…Since the direction of centrifugal force is completely parallel to the hollow fiber membrane, concentration polarization is avoided and the small molecules can pass through the membrane freely [24,25]. Furthermore, ignorable amount of ultrafiltrate is withdrawn from the hollow fiber compared with plasma sample in the slim glass tube, therefore, drug-protein binding equilibrium in plasma sample is stable, which would likely contribute to a more accurate result [21][22][23].…”

A study on characteristic of different sample pretreatment methods to evaluate the entrapment efficiency of liposomes

“…HF-CF-UF is mainly applied the pore size of hollow fiber to isolate accurately minor and micro molecules from complicated matrix under equilibrium state [27][28][29]. The centrifugal force is completely parallel to the hollow fiber membrane [16], which could eliminate the concentration polarization.…”