Fentanyl-Norfentanyl Concentrations During Transdermal Patch Application: LC-MS-MS Urine Analysis.

Area of Science:

• Clinical Chemistry
• Pharmacology
• Toxicology

Background:

• Previous research by Poklis and Backer established expected urine concentrations of fentanyl and norfentanyl from transdermal fentanyl patches using limited data.
• Gas Chromatography/Mass Spectrometry was the primary analytical method in the earlier study.

Purpose of the Study:

• To re-evaluate the accuracy of the original Poklis and Backer report on fentanyl and norfentanyl urine concentrations in a larger patient cohort.
• To develop a transformed model for urine drug test results yielding a near Gaussian distribution for clinical assessment.
• To provide physicians with a tool for evaluating expected patient values from urine drug testing.

Main Methods:

• Retrospective analysis of a larger population of patient urine samples positive for fentanyl and norfentanyl.
• Data transformation to normalize urine drug testing results.
• Development of a model to achieve a near Gaussian distribution of results.

Main Results:

• Confirmation that the original report's predictions for fentanyl and norfentanyl concentrations remain largely accurate over a decade later.
• Successful development of a transformed model resulting in a near Gaussian distribution of urine drug test results.
• The resulting distribution is dose-independent, offering a broad assessment of patient values.

Conclusions:

• The findings support the continued relevance of earlier predictions for fentanyl and norfentanyl urine levels in patients using transdermal fentanyl patches.
• The developed near Gaussian distribution model offers a valuable, dose-independent reference for physicians assessing patient urine drug test results.
• This model, when combined with clinical criteria, aids in evaluating patient adherence to treatment regimens.