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Pholcodine interference in the immunoassay for opiates in urine
Forensic Science International
|May 1, 1983
Summary
Pholcodine, a cough medicine ingredient, is excreted in urine for weeks, unlike other morphine drugs. This prolonged excretion detected by radioimmunoassay (RIA) can affect drug test results.
Area of Science:
- Pharmacology and Toxicology
- Analytical Chemistry
- Forensic Science
Background:
- Morphine derivatives are commonly used therapeutically, and their detection in biological samples is crucial for clinical and forensic purposes.
- Urine drug screening relies on accurate detection methods to identify substance use and interpret results correctly.
- Pholcodine is a widely used antitussive agent found in many cough preparations.
Purpose of the Study:
- To compare the urinary excretion profiles of pholcodine with other morphine derivatives (ethylmorphine, codeine) after therapeutic oral administration.
- To evaluate the performance of radioimmunoassay (RIA) and homogeneous enzyme immunoassay (EMIT) in detecting pholcodine metabolites in urine.
- To assess the clinical implications of prolonged pholcodine excretion on the interpretation of urine drug test results.
Main Methods:
- Analysis of urine samples from individuals receiving single oral therapeutic doses of ethylmorphine, codeine, and pholcodine.
- Quantification of opiates using radioimmunoassay (RIA) and homogeneous enzyme immunoassay (EMIT).
- Determination of the duration of positive opiate detection in urine for each drug.
Main Results:
- Ethylmorphine and codeine were rapidly excreted, with urine samples testing negative shortly after administration.
- Pholcodine showed prolonged positive results for opiates for 2-6 weeks when analyzed by RIA.
- Using EMIT, pholcodine yielded positive results for approximately 10 days, significantly shorter than RIA.
Conclusions:
- Pholcodine exhibits significantly longer urinary excretion of detectable opiate metabolites compared to ethylmorphine and codeine.
- The choice of immunoassay method (RIA vs. EMIT) critically impacts the detection window for pholcodine.
- The prolonged excretion of pholcodine poses a potential risk for misinterpretation of urine drug test results, necessitating awareness among clinicians and forensic toxicologists.