Microscale ultrafiltration technique for determining free drug in 50-microL serum samples

Area of Science:

• Pharmacokinetics
• Analytical Chemistry
• Biomedical Engineering

Background:

• Accurate determination of free drug concentrations is crucial for therapeutic drug monitoring.
• Existing ultrafiltration methods often require large sample volumes, limiting their use in specific populations.
• Pediatric and small animal studies necessitate methods with minimal sample requirements.

Purpose of the Study:

• To develop and validate a micro-scale ultrafiltration technique for free drug determination.
• To compare the efficacy of the modified micro-method with a standard micropartition system.
• To assess the suitability of the micro-method for various drug classes.

Main Methods:

• Ultrafiltration of serum samples containing valproic acid, phenobarbital, diazepam, indomethacin, phenytoin, furosemide, and chloramphenicol.
• Utilized a modified micro-system requiring 50 microL serum sample.
• Compared results with a commercially available micropartition system (MPS-1, Amicon) using 200 microL samples.

Main Results:

• The modified micro-ultrafiltration method demonstrated good agreement with the standard micropartition system for all tested drugs.
• The technique successfully determined free drug fractions with high accuracy.
• The method's low sample volume requirement was confirmed.

Conclusions:

• The developed 50 microL ultrafiltration technique provides a reliable and efficient method for free drug determination.
• This micro-method is particularly advantageous for pediatric and small laboratory animal studies.
• The technique offers a valuable tool for pharmacokinetic research and clinical applications requiring minimal sample volumes.