Ameritox

Welcome. Use of an algorithm applied to urine drug screening to assess adherence to an OxyContin® regimen.1

Objective

This study examined the ability of an algorithm applied to urine drug levels of oxycodone in healthy adult volunteers to differentiate among low, medium, and high doses of OxyContin®.

Participants & Interventions

Thirty-six healthy volunteers were randomized to receive 80, 160 and 240 mg of daily OxyContin® to steady state while under a naltrexone blockade. During days 3 and 4 of the study, urine samples of all participants were collected, and oxycodone levels detected in the urine were obtained using a liquid chromatography-mass spectrometry (LC-MS-MS) assay.

Outcome Measures

The concordance was calculated for raw and adjusted LC-MS-MS urine oxycodone values within each study participant between their third and fourth day values. Also, an analysis of medians was calculated for each of the dosage groupings using Bonett-Price confidence intervals for both raw and adjusted LC-MS-MS values.

Results

The concordance correlation coefficient for the raw LC-MS-MS values between days 3 and 4 was 0.689 (95% confidence intervals = 0.515, 0.864), whereas the concordance correlation coefficient for the LC-MS-MS values using the algorithm (i.e., normalized values) was 0.882 (95% confidence intervals = 0.808, 0.956).

Conclusions

In contrast to raw LC-MS-MS values, an algorithm that normalizes oxycodone urine drug levels for pH, specific gravity, and lean body mass discriminates well among all three of the daily doses of OxyContin® tested (80, 160 and 240 mg), even with correcting for multiple analyses.

Introduction

Although hydrocodone stands as the most prescribed opioid in the U.S., the opioid that is responsible for the most emergency department (ED) visits in the U.S. is oxycodone. According to the Drug Abuse Warning Network, approximately 77,000 ED visits in 2007 were due to the nonmedical use of oxycodone.2 The 2007 National Survey on Drug Use and Health estimates that 4.3 million Americans will abuse OxyContin® sometime during the course of their lifetime.3 Given the propensity for abuse of oxycodone-containing medications and the high incidence of ED visits associated with the abuse, monitoring patients for compliance while being prescribed a pain regimen is an important component of their care.

Previous studies have demonstrated the use of urine drug test results, when coupled with a compensatory algorithm, in approaching plasma methadone concentrations.4,5 This study examines the aforementioned oxycodone algorithm and its ability to differentiate among low, medium and high doses of OxyContin® using a highly sensitive liquid chromatography-mass spectrometry (LC-MS-MS) assay.