A Kinetic Approach to Determining Drug Distribution in Complex Biphasic Systems

Area of Science:

• Pharmaceutical Sciences
• Drug Delivery
• Physical Chemistry

Background:

• Pharmaceutical emulsions possess complex multiphase systems (micellar, aqueous, oil).
• Assessing bioequivalence of drugs in emulsions is challenging due to intricate drug transfer and equilibrium dynamics.
• Understanding drug distribution mechanisms is crucial for formulation development and regulatory approval.

Purpose of the Study:

• To develop a novel kinetic method for probing drug distribution mechanisms in biphasic systems.
• To quantify both the rate (kinetics) and extent (equilibrium) of drug partitioning.
• To provide a more flexible and insightful approach compared to traditional methods for complex formulations.

Main Methods:

• A kinetic method was developed based on biphasic diffusion principles.
• Drug partitioning was studied using three model compounds: triamcinolone acetonide, difluprednate, and cyclosporine.
• The kinetic method was validated against the traditional shake-flask method and tested with various organic/aqueous solvents.

Main Results:

• The kinetic method successfully determined drug distribution kinetics and equilibrium.
• Results from the kinetic and shake-flask methods showed good correlation (r² = 0.825) for model compounds.
• The kinetic method demonstrated flexibility with different solvent compositions, impacting drug distribution.

Conclusions:

• The developed kinetic method offers a robust approach to understanding drug distribution in complex biphasic pharmaceutical systems.
• This method provides enhanced insights into drug partitioning and potential drug release mechanisms.
• The kinetic approach facilitates more accurate bioequivalence assessments for emulsion-based drug products.