Send to

Choose Destination
See comment in PubMed Commons below
Eur J Pharm Sci. 2013 Jan 23;48(1-2):332-8. doi: 10.1016/j.ejps.2012.11.006. Epub 2012 Nov 28.

Effect of volume ratio of ultrafiltrate to sample solution on the analysis of free drug and measurement of free carbamazepine in clinical drug monitoring.

Author information

  • 1Department of Pharmaceutical Analysis, School of Pharmacy, Hebei Medical University, Shijiazhuang, Hebei Province 050017, China.


Traditional ultrafiltration (UF) usually has a large volume ratio of ultrafiltrate to sample solution, and this ratio cannot be well controlled. It can break the balance of protein-binding equilibrium and exert an influence on the analysis of free drug. In the present study, we evaluated the influence of volume ratio of ultrafiltrate to sample solution on the analysis of free drug in human plasma. We used carbamazepine as a model drug and studied the effect of different centrifugation times on ultrafitrate volume and the related effects on unbound carbamazepine measurement. Moreover, we compared the hollow fiber centrifugal ultrafiltration (HFCF-UF) with traditional UF. Our results showed that the ultrafiltrate volume was changed from 40 to 400 μL with the increase of centrifugation time for the traditional UF, and the related changes in unbound concentration were significant. The rate of protein binding (BP) was changed from 40% to 70%. In contrast, a tiny and invariant ultrafiltrate yield (40 μL) was obtained using the HFCF-UF method, and the BP rate was around 72%. In addition, with the HFCF-UF method, the volume ratio of ultrafiltrate to sample solution could be also well controlled by the inner diameters of both the glass tube and hollow fiber. The HFCF-UF method was a more accurate plasma pretreatment procedure, by which the in vivo balance of protein-binding equilibrium was hardly broken. Therefore, this method was successfully employed to quantify the free fraction of carbamazepine in clinical samples.

Copyright © 2012 Elsevier B.V. All rights reserved.

[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Elsevier Science
    Loading ...
    Write to the Help Desk