Urine Drug Screens

You should order a drug screen for any patient who has a substance use disorder,
or whom you suspect may have one. Drug screens are the key diagnostic
tests that help us determine what we are treating and whether our treatment
is successful. They are the only way to keep patients accountable for what they
tell you, because substance-using patients are often ashamed of their use and
hide the truth. Drug screening is not about “catching” or punishing patients.
Instead, it’s a way to help establish honesty and accountability.

At a minimum, you should order drug screens in the following
situations:
• Your patient has a current or recent substance use problem. This is the
major reason to get a drug screen: monitoring the sobriety of patients
who are acknowledged drug/alcohol users and want to get clean.
• Your patient has a remote substance use problem and you are considering
prescribing a medication with potential for abuse.
• Your patient is not improving despite receiving evidence-based treatment,
and you are wondering if drug use is interfering with treatment. The
estimated lifetime prevalence of drug or alcohol abuse in depression is
16%–27%, in bipolar disorder 43%–56%, and in schizophrenia 20%–65%,
depending on the study methodology used (Bradizza et al, 2006). The
lifetime prevalence of drug abuse in the general population is around 8%
(Compton et al, 2007), and around 18% for alcohol abuse (Hasin et al,
2007).
• You are prescribing a controlled substance medication (such as a psychostimulant
or a benzodiazepine) and your patient has been requesting early
refills or increased dosages.

WHICH TYPE OF SPECIMEN SHOULD YOU ORDER?
Specimens of urine, blood, hair, saliva, sweat, and even nails can be used
to do lab drug testing. See Table 2-1 for more detail on types of drug tests.

Most clinicians will order only urine testing.

TABLE 2-1. Available Drug Tests
Test Detection Time
Frame Notes
Urine 3–4 days Most commonly used
Blood 6–12 hours Can detect only recent drug use
Hair 7 days–3 months Expensive, but good for discovering use in
more distant past
Saliva 24 hours Convenient; patients can’t adulterate or
substitute; may not detect benzodiazepines
Sweat 7–14 days Patient can remove patch
Nails 7 days–3 months Not commonly ordered
Breathalyzer (for drugs: amphetamines, cocaine, marijuana, some opiates, and phencyclidine.
The comprehensive panel adds methadone (and sometimes other
opiates) and sedative/hypnotic medications, such as benzodiazepines, barbiturates,
and the “z-drugs” like zolpidem (Ambien) and zaleplon (Sonata).

 

Alcohol 7–12 hours
Alcohol metabolites, ethyl glucuronide
and ethyl sulfate (ETG/ETS)
3–4 days
Amphetamine/methamphetamine 1–2 days
Barbiturates 2–4 days (2–3 weeks for long-acting
phenobarbital)
Benzodiazepines 24 hours (short-acting); 2–4 days (longacting);
> 7 days for chlordiazepoxide,
diazepam
Cocaine 6–8 hours (2–4 days for benzoylecgonine
metabolite)
LSD 2–4 days
Marijuana 3 days for single use; 5–7 days for
moderate use (4x/week); 10–15 days for
daily use; > 30 days for long-term heavy
use
MDMA 1–2 days
Nicotine 12 hours
Opioids
• Codeine
• Buprenorphine
• Heroin, hydromorphone, morphine,
oxycodone
• Methadone
1–2 days
2–3 days (5–7 days metabolites)
2–4 days
2–3 days; 7–9 days for chronic use
PCP 2–8 days; up to 30 days for chronic use

 

Alcohol is not usually part of urine drug testing because it is only detectable
in the urine for a very short time—around 9 hours—depending on
the quantity and chronicity of alcohol consumption. Blood or breath alcohol
testing give a better idea of a person’s alcohol level, but the window of
detection is shorter.
With the various labs and collection methods, it can be difficult to decide
which test to order for which patient. Here’s my bottom-line advice:
• If you have no collection facility at your office, I suggest working with
TABLE 2-2. Urine Testing Detection Periods by Drug
Drug Detection Period for Urine Testing
Alcohol 7–12 hours
Alcohol metabolites, ethyl glucuronide
and ethyl sulfate (ETG/ETS)
3–4 days
Amphetamine/methamphetamine 1–2 days
Barbiturates 2–4 days (2–3 weeks for long-acting
phenobarbital)
Benzodiazepines 24 hours (short-acting); 2–4 days (longacting);
> 7 days for chlordiazepoxide,
diazepam
Cocaine 6–8 hours (2–4 days for benzoylecgonine
metabolite)
LSD 2–4 days
Marijuana 3 days for single use; 5–7 days for
moderate use (4x/week); 10–15 days for
daily use; > 30 days for long-term heavy
use
MDMA 1–2 days
Nicotine 12 hours
Opioids
• Codeine
• Buprenorphine
• Heroin, hydromorphone, morphine,
oxycodone
• Methadone
1–2 days
2–3 days (5–7 days metabolites)
2–4 days
2–3 days; 7–9 days for chronic use
PCP 2–8 days; up to 30 days for chronic use
Adapted from: Moeller KE et al, Mayo Clin Proc 2008;83(1):66–76.
Warner EA and Sharma N. Laboratory diagnosis. In Ries RK, Miller SC, Fiellen DA, Saitz R, eds.
Principles of Addiction Medicine. 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2009: 295–304.
Verebey KG and Meenan G, Diagnostic laboratory: screening for drug abuse. In Lowinson and Ruiz’s
Substance Abuse: A Comprehensive Textbook. Philadelphia: Wolters Kluwer, Lippincott Williams &
Wilkins, 2011.
22 THE CARLAT GUIDE SERIES | ADDICTION TREATMENT
one or more local lab collection sites. Large national laboratory service
companies such as LabCorp or Quest Diagnostics have multiple collection
sites in many areas and are usually set up to do urine collection for
drug testing. Which lab(s) you send patients to will often depend on the
individual patient’s health insurance. Just fill out a lab order requisition
(available online or through an electronic health record system) and give
it to the patient or send it to the lab.
• If you have a collection facility, the on-site lab can often help you determine
what tests to order.
Blood
Blood sampling is an accurate way of determining how much of a drug is in
a patient’s system, but its detection window is only 6–12 hours, so it’s hard
to use for random screens unless you can draw the sample in your office.
Hair
Hair analysis gives you a much wider detection window (up to 90 days) and
is an easy and noninvasive collection method. However, it won’t tell you
about your patient’s current substance use (it doesn’t detect use within the
previous 7–10 days), and it can’t detect alcohol use. Other limitations of hair
testing include difficulty in detecting low-level (single-time) use, and potential
inaccuracy depending on your patient’s hair color (some drugs have
enhanced binding to melanin in dark hair). While it’s hard to adulterate a
hair sample, some patients may bleach their hair or shave their head to avoid
this kind of testing; if so, hair on any other part of the body can be used.
Saliva
A quick swab of the inner cheek provides easy collection for saliva, which
can be used to detect traces of drugs and alcohol. Oral fluid testing is comparable
to urine testing and is less invasive; it’s also harder for patients to
adulterate or substitute. However, not all labs are equipped to test this type of sample.
Sweat
A skin patch that looks like a large adhesive bandage can be worn by patients
for up to 7–14 days to measure drugs in their sweat. This has become a popular
way for parole programs to monitor drug use. It’s noninvasive, easily
Chapter 2: DRUG TESTING 23
administered, and hard to adulterate (unless the patient removes the patch).
This method is limited by the availability of testing facilities; it’s also not
entirely clear whether its results are affected by how much a person sweats.
Commercial manufacturers have developed several wearable detection
devices to monitor blood alcohol level; these are primarily aimed at consumers
who are worried about getting a DUI, so they can plan to limit their
alcohol consumption or find a ride home.
Nails
Drug testing from nails is rare compared to testing of urine, hair, or oral
fluid. Similar to hair testing, nail testing has a long window of detection.
However, not many labs test nails, and there is insufficient scientific data to
support its routine use. Other limitations include the risk of environmental
contamination of nails for some drug classes; nail testing also cannot
detect alcohol.
Breath
Not every clinic needs an alcohol breathalyzer, but it can be helpful
if you think your patient has been drinking and you need to consider
safety issues (such as whether the patient should drive). The patient
blows into a breathalyzer device, which returns a number representing
the patient’s blood alcohol concentration. A breathalyzer’s detection
window is similar to blood testing (6–12 hours), but varies depending
on the amount of alcohol consumed over time. Some court systems
mandate alcohol breathalyzer ignition interlocks for the vehicles of DUI
offenders, which prevent the car from being started if the breath alcohol
level is too high.

alcohol only)
A few hours Often used by patient’s family to assess
driving safety
Urine
Urine drug testing is the most common test ordered because it’s noninvasive,
it’s available in large volume, and it generally has high concentrations
of drugs and metabolites (allowing for a longer detection time frame than
in blood, for example). Many factors can affect how soon and for how
long a drug can be detected, but you can make reasonable predictions. It
takes about 2–3 hours for most drugs to be concentrated in urine (only 30
minutes for alcohol), so testing too soon after use in a non-chronic user of
a drug may give you a negative result. Most drugs will be detected in urine
for about 2–4 days after use; some will be detected for longer (see Table 2-2
for urine testing detection windows).
Although labs vary, there are two common urine drug screening panels
that you can order: basic and comprehensive. The basic test screens for 5

 

Benzodiazepines
Not all benzodiazepines are detected on drug screens. Alprazolam and
diazepam, the most commonly misused benzodiazepines, are reliably
detected. Lorazepam and chlordiazepoxide are sporadically detected, and
clonazepam is often not picked up. Sometimes when I see unexpected
positive results for benzodiazepines, the patients are legitimately receiving
the medications from another doctor and do not realize they are potentially
abusable. I make sure they recognize the issue, and this usually offers a
teaching opportunity about the disadvantages of taking a benzodiazepine
while struggling with recovery from another drug.
Stimulants
Some OTC preparations can cause false positives for stimulants, such as
pseudoephedrine, but a patient will have had to ingest several boxes of it to
produce a false positive. Vicks VapoInhaler is an OTC product in a plastic
lipstick-size tube that contains levo-methamphetamine (a racemic isomer
of methamphetamine that is not psychoactive), which can cause a false
positive result for amphetamines. The cocaine assay is very reliable—there
are very few false positives, and it doesn’t cross-react with lidocaine or
Novocaine.
Phencyclidine
Phencyclidine (PCP) false positives are possible from dextromethorphan
in OTC cough medications, and from some antipsychotics.
False negatives
False negatives are more common than false positives, since patients
who are continuing to use despite treatment have a strong incentive to be
creative in efforts to mask their use—and there is a robust internet-based
industry catering to this market (see Table 2-4).
The most common way of achieving a false negative is water loading,
which I discussed earlier. There are various other readily available substances
that can be used to adulterate a urine sample. For example, patients
can add table salt to a sample, which can be effective, but if they add too
Chapter 2: DRUG TESTING 29
much it can precipitate out and make the effort obvious. Vinegar will
mask THC testing, but it lowers the pH of the urine sample, which will be
picked up on dipstick testing or by the lab in more formal testing. Other
specialized adulterants are available on the internet, usually selling for
about $19.99 per use. Some labs will test for the more common adulterants
like glutaraldehyde. The marketing for these products can be amusing. For
example, the product “Urine Luck” hired Tommy Chong (from Cheech
TABLE 2-4. False Negatives on Drug Screens
Potential Cause of False
Negative Drugs Masked Notes
Visine OTC eye drops
(tetrahydrozoline)
THC
benzodiazepines
Visine is squirted into urine
cup (squirting in eyes is not
effective for urine)
Drano or laundry bleach
(sodium hypochlorite)
amphetamine
barbiturates
benzodiazepines
cocaine
opiates
THC
Increases pH, but may
cause visible foam in urine
Vinegar (acetic acid) THC Lowers pH of urine sample
Ammonia multiple, depends on
assay
Increases pH, has
characteristic smell
Table salt (sodium chloride) amphetamine
barbiturate
cocaine
opiates
THC
Increases specific gravity of
urine sample (>1.035), may
precipitate out
Hydrogen peroxide THC
opiates
LSD
May cause bubbles in urine
Liquid hand soap multiple, depends on
assay
May cause bubbles or
make urine cloudy
Glutaraldehyde (UrinAid) cocaine
amphetamine
barbiturates
benzodiazepines
opiates
THC
Internet purchase, some
labs may test for this
adulterant
Pyridinium chlorochromate
(Urine Luck)
opiates
THC
Internet purchase
Potassium nitrite (Klear,
Whizzies)
THC Internet purchase
30 THE CARLAT GUIDE SERIES | ADDICTION TREATMENT
and Chong) to deliver the memorable slogan, “When you’re caught with
your pants down, Urine Luck.”