Determination of drug plasma protein binding by solid phase microextraction
Section snippets
INTRODUCTION
Determining the amount of drug binding to plasma proteins is an essential step in both drug discovery and in clinical phases of drug development. Binding of drugs to plasma proteins is important in understanding the pharmacokinetics and pharmacodynamic relationship of a drug.1., 2., 3. Therefore, plasma protein binding (PPB) is normally recognized as an important factor in assessing drug disposition, efficacy, and safety.4 In the early drug development stage, the knowledge of drug protein
Chemicals and Reagents
Verapamil (99%), propranolol (99%), warfarin (98%), ibuprofen (99%), lithium perchlorate (95%), pyrrole (98%), PBS pouches, and acetic acid were purchased from Sigma (Mississauga, ON, Canada); ammonium acetate, acetone, and nitric acid were obtained from BDH, Inc. (Toronto, ON, Canada); caffeine (99%) was obtained from Aldrich (Mississauga, ON, Canada); diazepam standard (1 mg/mL in methanol, 98%) was purchased from Cerilliant (Austin, TX); HPLC grade acetonitrile and methanol were purchased
EXPERIMENTAL RESULTS AND DISCUSSION
Experiments were carried out in 2 mL vials with polypropylene inserts. For increased throughput, the inserts can be arranged in standard 96-well format. After the inserts were filled with sample or desorption solution, the SPME fibers were introduced through the vial septum and the whole assembly was incubated and/or shaken.
Five well-studied drugs (ibuprofen, warfarin, verapamil, propranolol, and caffeine) with a wide range of physicochemical properties were selected for evaluating the
CONCLUSIONS
Due to the important clinical implications of plasma protein binding data and its role in characterizing a drug's behavior and proper dosing, there is an increasing need to make this measurement as early as possible in the discovery process in order to understand drug disposition and to optimize individual drug therapy.
This study details a new method for determining the value of PPB based on the partitioning of a drug between an SPME fiber and plasma proteins. The suitability of this method was
Acknowledgements
Authors gratefully acknowledge the financial support of Millennium Pharmaceuticals (Cambridge, MA) and the Natural Sciences and Engineering Research Council of Canada.
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2023, International Journal of PharmaceuticsRapid equilibrium dialysis, ultrafiltration or ultracentrifugation? Evaluation of methods to quantify the unbound fraction of substances in plasma
2023, Biochemical and Biophysical Research CommunicationsRecent advances in the determination of unbound concentration and plasma protein binding of drugs: Analytical methods
2021, TalantaCitation Excerpt :Conventional SPME coatings such as polyacrylate (PA), polydimethylsiloxane (PDMS) and carbowax (CW) provided high extraction efficiency for neutral compounds or neutral species of ionizable compounds. On the other hand, a study has shown that due to changes in plasma pH, the ionization degree of ionizable compounds changes, consequently the sorption of neutral species of these compounds to the SPME fiber is severely affected and can alter the protein binding of drugs [31]. Besides, for ionized compounds with high PB, extraction from a small fraction of neutral species that are freely available could lead to detection problems.
Method for Simultaneous Determination of Free Concentration, Total Concentration, and Plasma Binding Capacity in Clinical Samples
2021, Journal of Pharmaceutical SciencesCitation Excerpt :Once the concentrations of binding proteins were used as co-variates to correct the values of total concentrations determined by UF, accounting for 0.32% assumed leakage of binding proteins, the corrected values had a stronger correlation (R2 = 0.9325) with concentrations obtained by protein precipitation; furthermore, the slope improved from 0.5663 to 1.0131 (Fig. 2b). The free testosterone concentration was determined by both ST and UF approaches and were found to be reasonably well correlated, with R2 = 0.9102; however, the slope of the correlation was lower than one, indicating that ST results are lower than those obtained with UF – in agreement with the assumption that some binding proteins leaked through the UF membrane, resulting in a slight overestimation of the free concentration (Fig. 3). The plasma binding capacity (PBC) of the volunteer samples determined using the two newly proposed methods (with addition of labeled analyte) were well correlated (r = 0.7282) and achieved statistical significance, but the slope of the relationship was considerably less than one (Table 4).