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Updated: Jun 23, 2026

High-throughput and Comprehensive Drug Surveillance Using Multisegment Injection-Capillary Electrophoresis-Mass Spectrometry
Published on: April 23, 2019
Efavirenz treatment and false-positive results in benzodiazepine screening tests
Antje Blank1, Victoria Hellstern, Dieter Schuster
1Department of Internal Medicine VI, Clinical Pharmacology and Pharmacoepidemiology, University Hospital Heidelberg, Heidelberg 69120, Germany.
Abstract:
We investigated the effect of efavirenz treatment on the results of drug screening tests of urine samples obtained from 100 patients infected with human immunodeficiency virus. Of 50 patients who received efavirenz, 49 tested positive for benzodiazepines in > or =1 drug screening test, whereas of 50 patients who did not receive efavirenz, only 1 tested positive for benzodiazepines in > or =1 drug screening test. The major metabolite 8-hydroxy-efavirenz is responsible for this cross-reactivity.
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