Input rate-dependent stereoselective pharmacokinetics: effect of pulsatile oral input

Area of Science:

• Pharmacokinetics and Drug Metabolism
• Computational Chemistry and Modeling

Background:

• Stereoselectivity in drug metabolism is crucial for chiral drugs.
• Understanding how drug input affects enantiomer concentrations is vital for accurate bioequivalence assessments.

Purpose of the Study:

• To investigate the impact of pulsatile oral input on the stereoselectivity of racemic drugs.
• To analyze how dose, dosage interval, and formulation influence enantiomeric drug concentrations and bioequivalence.
• To evaluate the reliability of bioequivalence studies for chiral drugs with nonlinear metabolism.

Main Methods:

• Computer simulations were employed to model pulsatile oral drug administration.
• Simulations considered Michaelis-Menten hepatic metabolism with varying enantiomeric Vmax and Km values.
• Both steady-state and nonsteady-state conditions were simulated.

Main Results:

• Pulsatile input determinants (dose, interval, formulation) significantly affected enantiomeric AUC ratios.
• Changes in enantiomeric AUC ratios showed opposite trends for drugs with different Vmax versus Km values.
• Nonsteady-state and steady-state analyses yielded different conclusions regarding stereoselectivity.
• Simulations indicated potential for erroneous bioequivalence conclusions when relying solely on racemic drug measurements.

Conclusions:

• Input rate-dependent stereoselective pharmacokinetics can complicate bioequivalence assessments for chiral drugs.
• Experimental designs for evaluating stereoselective pharmacokinetics and bioequivalence should account for pulsatile input characteristics.
• The study provides a framework for optimizing experimental designs in preclinical and clinical settings.