Acceptable sampling times at plateau for drug analysis

Area of Science:

• Pharmacokinetics
• Clinical Pharmacology
• Biomedical Engineering

Background:

• Accurate estimation of average plasma drug concentration at plateau (Cav) is crucial for effective therapeutic drug monitoring.
• Current methods may lack precision due to patient variability and assay limitations.

Purpose of the Study:

• To evaluate two methods for estimating Cav.
• To determine optimal blood sampling time strategies for accurate Cav estimation.
• To identify factors influencing the precision of Cav estimates.

Main Methods:

• Analysis of pharmacokinetic principles for drug concentration monitoring.
• Calculation of acceptable error ranges for Cav estimates.
• Modeling the impact of half-life variability, dosing interval, and assay error on sampling strategies.

Main Results:

• A range of sampling times, rather than a single point, can be determined for a given acceptable error in Cav estimation.
• This sampling time range is influenced by population half-life variability, dosing interval, assay measurement error, and drug therapeutic index.
• Monitoring minimum plasma drug concentration requires individual half-life estimation unless the dosing interval is short, in which case population half-life may suffice.

Conclusions:

• Flexible blood sampling strategies improve the accuracy of average plasma drug concentration (Cav) estimation.
• Understanding pharmacokinetic variability is key to optimizing drug dosing and monitoring.
• The proposed methods offer a more robust approach to therapeutic drug monitoring, especially for drugs with narrow therapeutic indices.