Premium on Safety - Issue 42 2021 - 3

BEST PRACTICES
COMMON CAUSES OF FALSE POSITIVES
There are many commonly used prescription and over the counter
(OTC) medications that are allowed by the FAA that may cause
a false positive urine test. There are five categories (besides
cannabinoids as mentioned earlier) of medications that cause
false positive drug levels. The categories of main concern to the
pilot and civilian population are: amphetamines, benzodiazepines,
opioids, PCP, and tricyclic antidepressants. All amphetamine
medications are disallowed for pilot use by the FAA.
Medications that could cause a falsely elevated amphetamine
level are metformin, labetalol, pseudoephedrine, and ranitidine.
Metformin (Glucophage®) is a medication used in diabetes type
Urine testing for drugs is faster and cheaper
but has a higher false positive rate than
blood testing or other more technologically
advanced tests.
II for glycemic control. Pseudoephedrine (Sudafed®) is an OTC
medication taken for nasal congestion. Pseudoephedrine is also
manufactured in combination with non-sedating antihistamines
like Claritin-D (loratadine and pseudoephedrine), Allegra-D®
(fexofenadine and pseudoephedrine), and Zyrtec-D (certirizine
and pseudoephedrine). Labetolol (Normodine®) is a beta-blocker
medicine that mainly controls the patient's heart rate. Labetolol
is used for hypertension and is indicated in hypertensive urgency
when the blood pressure is very high for long periods of time.
Ranitidine (Zantac®) is an H2 blocking agent used for ulcers and
gastroesophageal reflux disease (GERD). Ranitidine is available
OTC so be aware that chronic use could possibly cause a false
positive urine test for amphetamine.
Benzodiazepines are medications used in patients with anxiety.
They include diazepam (Valium®), lorazepam (Ativan®), and
alprazolam (Xanax®). All benzodiazepines are no-fly medications.
Medications that could cause a falsely elevated benzodiazepine
level are Sertraline, Oxaprozin, and Efavirenz. Sertraline
(Zoloft®) is an FAA-allowed serotonin reuptake inhibitor (SSRI)
for depression that requires a Special Issuance Authorization.
Oxaprozin (Daypro®) is a non-steroidal anti-inflammatory (NSAID)
that is used for pain and inflammation. Efavirenz (Sustiva®) is an
antiviral medication prescribed for patients with HIV.
We know there is an opioid crisis in the United States. Pain
medications that contain opioids including codeine, morphine,
oxycodone, and hydrocodone-when used chronically-have
a high abuse potential. Medications that could cause a falsely
elevated opioid level include dextromethorphan, quinolones, and
verapamil. Dextromethorphan is an active ingredient in many
OTC cough and cold products and in high doses may cause
hallucinations. Quinolones are antibiotics that are prescribed to
treat pneumonia, skin infections, sinus infections, and urinary tract
infections. Quinolone antibiotics that are commonly prescribed
are Levofloxacin (Levoquin®), ciprofloxacin (Cipro®), and ofloxacin
(Floxin®). Verapamil (Verelan PM®) is a calcium channel blocking
agent used to control heart rate in patients with atrial fibrillation
and blood pressure in patients with hypertension.
Phencyclidine (PCP) is a hallucinogen found in a street drug
called Angel Dust. Medications that may cause a falsely elevated
PCP level are Dextromethorphan, diphenhydramine, doxylamine,
ibuprofen, and tramadol. Diphenhydramine (Benadryl®) is an OTC
long-acting antihistamine found in many different combination
products for seasonal allergies. In my humble opinion, no pilot
should ever use diphenhydramine for seasonal allergies or for
sleep (Tylenol PM). It is on " Larry's NEVER to take list. " The
sedative effect of this antihistamine ( " hangover effect " ) is a no-go
for flight. Diphenhydramine takes 60 hours to be eliminated
from the body. Doxylamine (Unisom®) is an OTC sleep aid that is
on the FAA no-fly list. Ibuprofen (Motrin®) is an NSAID used for
pain and inflammation. Tramadol (Ultram®) and tramadol with
acetaminophen (Ultracet®) are pain medications that work on
the same receptors as opiates. Please see the FAA medication
database on aopa.org for specific prescribing criteria and the
48-hour wait period before flying after taking tramadol.
Tricyclic antidepressants (TCAs) are the first generation of
medications used for depression and are rarely used in healthcare
nowadays. This category of medications caused many side effects
that included cardiac arrhythmias. Diphenhydramine can cause a
false elevation urine test for TCA.
BEST PRACTICES
Do not take medications that are prescribed for someone else.
Always have your updated medication record available that can be
supplied to your primary care provider and all specialists. Inform
your provider of all OTC medications you are taking. Ensure that
all of your currently prescribed and OTC medications are included
when renewing your medical.
I hope you never have to be the receiver of a falsely positive
urine drug test. The impact on your license and medical can
be significant.
There is an alternate testing method to distinguish if a urine test is a
true false positive or true positive result. Gas chromatography-mass
spectrometry (GCMS) or high-performance liquid chromatography
(HPLC) are more sensitive than the typical urine tests.
Pilots know that knowledge is power and this rarely studied
phenomenon is another tool in your pilot toolbox. Be well and
be safe.
-Larry Diamond has a Doctor of Pharmacy Degree and has
been a pharmacist for 37 years. Larry's pharmacy practice
has been as a Clinical Pharmacy Specialist in Cardiology,
Orthopedic Surgery Specialist and most recently Clinical
Pharmacy Coordinator. He is a CFII, a pilot for 33 years and
has been an AOPA member since 1984.
This article was first published online as a two-part article June
2021 and August 2021, for AOPA Pilot Protection Services.
3
https://www.aopa.org/go-fly/medical-resources/medications-database https://pilot-protection-services.aopa.org/

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