An HIV-positive patient receiving efavirenz may have a positive urine drug screening test with positive results for benzodiazepines and/or tetrahydrocannabinol (THC).
Efavirenz is a non-nucleoside reverse-transcriptase inhibitor that is used in highly active antiretroviral therapy (HAART) drug regimens.
Test
Cause
benzodiazepines
8-OH-efavirenz
tetrahydrocannabinol
glucuronidated structure of efavirenz metabolites
Clinical features:
(1) positive urine drug screen showing benzodiazepine or THC
(2) negative confirmation test (GC-MS, other)
(3) history of efavirenz drug therapy at time of urine drug test
(4) negative urine drug test if efavirenz therapy interrupted for several days (although this may be undesirable for a person on HAART)
This underlies the need to wait for confirmation before acting on any urine drug screening test.
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