American Society of Regional Anesthesia and Pain Medicine November 2017 - 28
Urine Drug Screens for Opioid Maintenance: Is It That Simple?
CASE PRESENTATION
A 54-year-old male presented to the pain medicine center for
evaluation of chronic neck pain and transfer of medication
management. He was taking oxymorphone extended-release (ER)
tablets 10 mg twice a day and one to two tablets of oxycodone 10
mg per day. The state prescription monitoring program confirmed
his prescriptions of 60 tablets of oxymorphone ER 10 mg and 150
tablets of oxycodone 10 mg, filled monthly. His last prescription
was filled 25 days prior. When asked about how much remaining
oxycodone he has, he replied that he only had a few tabs left. He
added that he had taken one tab of oxymorphone and one tab of
oxycodone in the morning prior to his arrival at the clinic. A urine
sample was taken, and the results are reported in the Table.
He is MOST likely taking which of the following?
A.
B.
C.
D.
He is taking oxymorphone and oxycodone.
He is taking oxymorphone, oxycodone, and morphine.
He is taking oxymorphone, oxycodone, and heroin.
He is taking oxymorphone.
"A great man once said that the true symbol of the United States
is not the bald eagle. It is the pendulum. And when the pendulum
swings too far in one direction, it will go back."
- Ruth Bader Ginsberg
Nearly one-third of the American population has experienced or
is living in chronic pain, defined as pain that is persistent and
lasts more than 3 to 6 months. Over the past several decades, the
development of opioid medications for the treatment of pain has
increased dramatically. With this increase, we have seen yearly
prescriptions of opioids catapult from 76 million to greater than 250
Table 1: Lab results.
Opiate
Qualitative
lab result
Lab result
(ng/mL)
Assay cutoff
(ng/mL)
Opiates
Positive
458
50
Codeine
Negative
Morphine
Positive
Hydrocodone
Negative
100
Hydromorphone
Negative
100
Norhydrocodone
Negative
100
Oxycodone
Negative
100
Oxymorphone
Positive
Noroxycodone
Negative
28
100
252
1423
100
100
100
million over a 20-year period,1
which, unfortunately, is directly
correlated with an increase in
opioid abuse.2 In response to this
increase in opioid maintenance,
dependence, and addiction,
the Centers for Disease Control
and Prevention (CDC) published
guidelines for the prescribing of
opioids for chronic pain in March
2016.3
Geeta Nagpal, MD
With the growing epidemic,
Program Director, Multidisciplinary
providers must effectively monitor
Pain Medicine Fellowship
the use of prescription opioids to
Assistant Professor, Department of
identify misuse, addiction, and
Anesthesiology
diversion. Some examples of
Northwestern University, Feinberg
the tools available include state
School of Medicine
prescription drug monitoring
Evanston, Illinois
programs and urine drug testing.
There are two fundamental
Section Editor: Lynn Kohan
questions that lead a clinician
to order a urine drug screen
(UDS): (1) Is the patient taking the prescribed medication, and (2)
is the patient abstaining from the use of nonprescribed controlled
and illicit substances? The CDC suggests obtaining a UDS before
the initiation of opioid treatment and to consider screening at
least annually. However, the interpretation of drug testing is far
less straightforward than expected, yet the ramifications can be
significant. Occasionally, it can be difficult to interpret a result as
normal or abnormal based on opioid compounds found in the urine.
Misinterpreting results can lead to false reassurance or incorrect
conclusions about medication use and abuse.
Accurate interpretation of a UDS requires knowledge of urine
metabolites, specificities and sensitivities of the assay, and
detection times. Some opioids produce metabolites chemically
identical to another opioid, which may complicate the interpretation
of the UDS. A common example is codeine, a prodrug that
metabolizes to morphine in approximately 90% of Caucasian
patients.4 Interestingly, in a 2007 survey of physicians who
routinely order UDSs, only 29% knew that morphine is a metabolite
of codeine and should be expected on UDSs in patients taking
codeine.5 In a more recent study of knowledge and confidence in
UDS interpretation of internal medicine residents, less than 30%
correctly answered what the expected metabolites would be in a
patient prescribed acetaminophen/codeine.6 Unfortunately, many
were confident in their incorrect response.
Incorrect conclusions may also be drawn from ordering
inappropriate tests. UDSs are most commonly performed using
immunoassays or mass-spectrometry. Opiate immunoassays are
American Society of Regional Anesthesia and Pain Medicine
2017
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