Limitations of Drug Screens
From a practical viewpoint it is impossible to determine in every case
that a given individual is impaired in the workplace due to drug abuse.
Just as in the case of alcohol, the use of drugs spans a wide spectrum of
behavior, from the occasional recreational user who assiduously avoids
coming to work under the influence, to the hard-core addict whose only
motivation is the acquisition of his or her next dose. Generally the
clinical laboratory is not able to distinguish these two types of
individuals. Such a distinction comes about only by careful evaluation by
professionals specially trained in the psychology and physiology of drug
abuse. The laboratory should be used only as a helpful tool for such
professionals.
Urine drug screens panels are set up to analyze urine for a variety of
drugs that are known to have high abuse potential and affect task
performance.
To rule out the presence of all drugs that may impair a worker's
performance is not generally allowable within the bounds of cost
containment. Certain drugs which are not usually picked up on routine drug
screens are noted below. If intoxication by any of the drugs listed below
is suspected, it is recommended that the client contact the B&A
pathologist, who will be glad to help determine a strategy as to how the
case should be most efficiently handled.
Methylphenidate (Ritalin), phentermine (Fastin, Parmine), phenmetrazine
(Preludin), phendimetrazine (Plegine), diethylpropion (Tenuate),
mazindol (Mazanor, Sanorex), benzphetamine (Didrex) and fenfluramine
(Pondimin) all have amphetamine-like effects and abuse potential. Some of
them, such as phentermine, benzphetamine, fenfluramine and diethylpropion,
may not be picked up on routine screens.
Methylenedioxyamphetamine (MDA, "Ecstasy") is has been popular in
Houston high schools. Although it is technically an amphetamine, it
requires a special analysis to be identified.
Lysergic acid diethylamide (LSD) is also chemically related to the
amphetamines, but it is much better known for its profound
hallucinogenic effects. Special analysis is available.
Meperidine (Demerol) and pentazocine (Talwin) have physiological effects
and abuse potential essentially identical to those of opiates. However,
since they are chemically dissimilar to morphine, they may not show up as
"opiates" on a routine screen. Special analysis is available.
Barbiturates which are not easily detected on drug screens include
amobarbital (Amytal), pentobarbital (Nembutal), and butethal. The detection
systems used to pick up barbiturates are optimized for secobarbital
(Seconal), which is probably the most important barbiturate in abusing
populations.
Flurazepam (Dalmane), a benzodiazepine used as a sleeping pill, is not
ordinarily picked up on benzodiazepine screens.
Glutethimide (Doriden), ethchlorvynol (Placidyl), meprobamate (Miltown,
Equanil), methyprylon (Noludar), and ethinamate (Valmid) are sedative
drugs that can produce dependence and impaired function. Although they may
have some effects similar to those of the barbiturates, they are chemically
unrelated and must be detected with special procedures.
Hydrocarbon solvents. These are inhaled by glue sniffers to produce a
euphoric effect. Although this seems to be less of a problem socially now
than in previous years, special analysis of hydrocarbons and chlorinated
hydrocarbons is available.
Ketamine (Ketalar), chemically related to phencyclidine (PCP), is used
as a general anesthetic but has been abused, often by health care workers.
It must be injected for effect. Analysis is available only through
specialized laboratories, and turnaround time is typically long.
Designer opiates. These, like meperidine, are synthetic analogues of
natural opiates. Accordingly, their chemical structure may be so alien to
that of natural opiates that they go completely undetected. These are
medically very significant drugs. For instance, 3-methylfentanyl ("China
white") is 3000 times as potent as morphine and has been responsible for
over 100 overdose deaths in California. Another, 1-methyl-4-
phenylpropionoxypiperidine (MPPP), may be contaminated with an unintended
byproduct (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine, or MPTP) which
destroys the substantia nigra of the brain and produces permanent
parkinsonism.
Adulteration of urine samples with such substances as lemon juice,
vinegar, chlorine bleach, and NaCl has been used to successfully interfere
with detection of cannabinoids. Also, marked overhydration of the subject
(by quaffing large volumes of water) may so dilute the urine that the
concentration of the telltale metabolite falls below the detection
threshold of the screen.
that a given individual is impaired in the workplace due to drug abuse.
Just as in the case of alcohol, the use of drugs spans a wide spectrum of
behavior, from the occasional recreational user who assiduously avoids
coming to work under the influence, to the hard-core addict whose only
motivation is the acquisition of his or her next dose. Generally the
clinical laboratory is not able to distinguish these two types of
individuals. Such a distinction comes about only by careful evaluation by
professionals specially trained in the psychology and physiology of drug
abuse. The laboratory should be used only as a helpful tool for such
professionals.
Urine drug screens panels are set up to analyze urine for a variety of
drugs that are known to have high abuse potential and affect task
performance.
To rule out the presence of all drugs that may impair a worker's
performance is not generally allowable within the bounds of cost
containment. Certain drugs which are not usually picked up on routine drug
screens are noted below. If intoxication by any of the drugs listed below
is suspected, it is recommended that the client contact the B&A
pathologist, who will be glad to help determine a strategy as to how the
case should be most efficiently handled.
Methylphenidate (Ritalin), phentermine (Fastin, Parmine), phenmetrazine
(Preludin), phendimetrazine (Plegine), diethylpropion (Tenuate),
mazindol (Mazanor, Sanorex), benzphetamine (Didrex) and fenfluramine
(Pondimin) all have amphetamine-like effects and abuse potential. Some of
them, such as phentermine, benzphetamine, fenfluramine and diethylpropion,
may not be picked up on routine screens.
Methylenedioxyamphetamine (MDA, "Ecstasy") is has been popular in
Houston high schools. Although it is technically an amphetamine, it
requires a special analysis to be identified.
Lysergic acid diethylamide (LSD) is also chemically related to the
amphetamines, but it is much better known for its profound
hallucinogenic effects. Special analysis is available.
Meperidine (Demerol) and pentazocine (Talwin) have physiological effects
and abuse potential essentially identical to those of opiates. However,
since they are chemically dissimilar to morphine, they may not show up as
"opiates" on a routine screen. Special analysis is available.
Barbiturates which are not easily detected on drug screens include
amobarbital (Amytal), pentobarbital (Nembutal), and butethal. The detection
systems used to pick up barbiturates are optimized for secobarbital
(Seconal), which is probably the most important barbiturate in abusing
populations.
Flurazepam (Dalmane), a benzodiazepine used as a sleeping pill, is not
ordinarily picked up on benzodiazepine screens.
Glutethimide (Doriden), ethchlorvynol (Placidyl), meprobamate (Miltown,
Equanil), methyprylon (Noludar), and ethinamate (Valmid) are sedative
drugs that can produce dependence and impaired function. Although they may
have some effects similar to those of the barbiturates, they are chemically
unrelated and must be detected with special procedures.
Hydrocarbon solvents. These are inhaled by glue sniffers to produce a
euphoric effect. Although this seems to be less of a problem socially now
than in previous years, special analysis of hydrocarbons and chlorinated
hydrocarbons is available.
Ketamine (Ketalar), chemically related to phencyclidine (PCP), is used
as a general anesthetic but has been abused, often by health care workers.
It must be injected for effect. Analysis is available only through
specialized laboratories, and turnaround time is typically long.
Designer opiates. These, like meperidine, are synthetic analogues of
natural opiates. Accordingly, their chemical structure may be so alien to
that of natural opiates that they go completely undetected. These are
medically very significant drugs. For instance, 3-methylfentanyl ("China
white") is 3000 times as potent as morphine and has been responsible for
over 100 overdose deaths in California. Another, 1-methyl-4-
phenylpropionoxypiperidine (MPPP), may be contaminated with an unintended
byproduct (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine, or MPTP) which
destroys the substantia nigra of the brain and produces permanent
parkinsonism.
Adulteration of urine samples with such substances as lemon juice,
vinegar, chlorine bleach, and NaCl has been used to successfully interfere
with detection of cannabinoids. Also, marked overhydration of the subject
(by quaffing large volumes of water) may so dilute the urine that the
concentration of the telltale metabolite falls below the detection
threshold of the screen.
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