Phenytoin pharmacokinetic analysis and steady-state level prediction using a programmable calculator

Area of Science:

• Pharmacokinetics
• Computational Chemistry
• Clinical Pharmacology

Background:

• Accurate determination of drug metabolism parameters is crucial for effective therapeutic drug monitoring.
• The Michaelis-Menten model describes saturable drug metabolism, common for drugs like phenytoin.
• Individualized pharmacokinetic parameter estimation can optimize drug dosing and reduce adverse effects.

Purpose of the Study:

• To describe a method for determining individualized Michaelis-Menten parameters for phenytoin using a programmable calculator.
• To develop a predictive tool for phenytoin steady-state concentrations based on patient-specific parameters.

Main Methods:

• Utilized a programmable calculator (HP-97) for pharmacokinetic calculations.
• Employed linear regression analysis to fit dose and steady-state concentration data to a linear-transformed Michaelis-Menten equation.
• Solved for individual Michaelis-Menten parameters (Vmax and Km).

Main Results:

• Successfully determined individualized Michaelis-Menten parameters for phenytoin.
• Developed a calculator program capable of predicting steady-state phenytoin concentrations for given doses.
• Demonstrated the utility of a programmable calculator for complex pharmacokinetic analysis.

Conclusions:

• Programmable calculators can be effectively used for determining individualized Michaelis-Menten parameters.
• This approach facilitates personalized phenytoin dosing strategies.
• The developed method offers a practical tool for clinical pharmacokinetic applications.