Constant-Speed Intravenous Infusion Model Determines Pharmacokinetic Parameters: Phylloquinone as an Example

Area of Science:

• Pharmacokinetics
• Drug Metabolism and Disposition
• Vitamin K Research

Background:

• Classical pharmacokinetic models exhibit significant variability in phylloquinone half-life (t1/2) due to limitations.
• Low terminal-phase concentrations after Intravenous (IV) bolus administration complicate accurate parameter estimation.

Purpose of the Study:

• To determine phylloquinone pharmacokinetic parameters using a Constant-Speed Intravenous Infusion (CSII) strategy.
• To overcome limitations associated with terminal-phase data in traditional IV bolus analyses.

Main Methods:

• Sprague-Dawley rats received a 15-hour constant-rate infusion of phylloquinone.
• Plasma concentrations were measured using High-Performance Liquid Chromatography (HPLC).
• Pharmacokinetic parameters were derived by fitting data to a one-phase exponential association model.

Main Results:

• CSII yielded a phylloquinone half-life (t1/2) of 4.27 ± 0.47 h, clearance (CL) of 56.93 ± 9.00 mL/h, and volume of distribution (Vd) of 321.86 ± 29.25 mL.
• CSII avoided issues with low terminal-phase concentrations, providing robust parameter estimates.
• Estimated Vd after CSII was larger than that obtained from IV bolus administration.

Conclusions:

• The CSII strategy enables robust pharmacokinetic parameter estimation from the ascending concentration phase, bypassing problematic terminal-phase data.
• This method clarifies inconsistencies found with traditional IV bolus analyses for phylloquinone.
• CSII is a valuable complementary approach for compounds with challenging terminal-phase analysis or those administered via continuous infusion.