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by Rick Bayer, (Source:Alternatives)
05 Oct 2005
Oregon
What Are the Facts:
Does cannabis alone, inhaled eight or more hours before activities such as
driving a vehicle or working with machinery, cause significant mental or
motor impairment that might increase risk to self or others? This is the
question, properly stated, that legislators should have considered during
the session just ended.
Instead, during the 2005 legislative session, Oregon House Bill 2693 passed
the Republican-controlled House. HB 2693 would allow employers to
fire--without evidence of impairment--Oregonians who register with the
Oregon Medical Marijuana Program and who use marijuana as medicine.
Fortunately the house bill failed in a Democrat-controlled Senate committee
after heated testimony, but this may be a temporary reprieve as this
impaired piece of legislation will probably be introduced again in the next
round.
Marijuana as Medicine
Cannabis has been used to relieve pain for centuries throughout the world,
including in the US, prior to the Cannabis Tax Act of 1937. Cannabis-like
compounds are called cannabinoids. The cannabinoid that most affects mental
status, the one that has "psychoactive" effects, is THC, or
tetrahydrocannabinol. THC is a highly effective pain reliever, equal in
efficacy to codeine. GW Pharmaceuticals has performed randomized
double-blind placebo-controlled trials showing that Sativex ( a cannabis
extract now available in Canadian pharmacies ) markedly improves pain. For
more on Sativex, see Alternatives Magazine Spring 2005 issue:
www.alternativesmagazine.com/33/bayer.html. Perhaps the best summary
regarding pain relief is from the prestigious Institute of Medicine; "In
conclusion, the available evidence from animal and human studies indicates
that cannabinoids can have a substantial analgesic effect."
The Oregon Medical Marijuana Act ( OMMA ), passed in 1998, states, " . .
. marijuana should be treated like other medicines." Once inside the body,
THC acts identically whether it comes from herbal cannabis or from synthetic
Food and Drug Administration-approved THC ( Marinol, brand of dronabinol ).
Either way, the major psychoactive cannabinoid remains THC so let's examine
how THC is metabolized and experienced by the human body.
Marijuana and Impairment
In A Primer of Drug Action, pharmacologist Robert Julian, MD, PhD, wrote, "
. . . absorption of inhaled drugs is rapid and complete. The onset of
behavioral effects of THC in smoked marijuana occurs almost immediately
after smoking begins and corresponds with the rapid attainment of peak
concentrations in plasma. Unless more is smoked, the effects seldom last
longer than 3 to 4 hours."
In the Journal of Cannabis Therapeutics, Franjo Grotenhermen, MD, wrote,
"Pulmonary [lung] assimilation of inhaled THC causes a maximum plasma
concentration within minutes, while psychotropic effects [the "high"] start
within seconds to a few minutes, reach a maximum after 15 to 30 minutes, and
taper off within 2 or 3 hours."
In summary, any mental or motor "impairment" is associated with the
psychotropic effects ( the "high" ), and these effects are equally
associated with pain relief. When the plasma THC levels return to
low-levels at 3 hours and baseline around 4 hours after smoking marijuana,
the high resolves, and so too does any impairment. This is important: no
impairment after 3 or 4 hours from taking THC.
Marinol is available only by mouth but the package insert warnings should be
heeded regardless of whether a person uses Marinol or herbal THC. These
include: WARNINGS: Patients receiving treatment with Marinol should be
specifically warned not to drive, operate machinery, or engage in any
hazardous activity until it is established that they are able to tolerate
the drug and perform such task safely. This is sound advice.
When a clinician monitors drug therapy--any drug therapy--s/he educates a
patient through careful explanations of procedures ( method of use and
expected results ), alternative therapies, and risks involved in using or
not using a medicine. There are many medicines--prescription or
nonprescription--that cause drowsiness or impairment. These include
medicine for blood pressure, diabetes, arthritis, respiratory infection,
allergies, mood stabilization, and pain. Good communication lessens risks
of adverse drug reactions.
Whether in a workplace or not, one should avoid impairment when driving,
operating machinery, or engaging in any hazardous activity. If the goal is
safety, there is no substitute for actual observation of performance because
impairment can have many sources. Non-prescription medicines, acute
illness, or sleep loss can result in impairment. Good communication between
employees, supervisors, and employers lessens risk of impairment at work.
With all of the above in mind, here is the crux of the problem so
ineffectively addressed by the sponsors of House Bill 2693. The standard
urine test for "marijuana" does not test for the psychoactive "parent drug",
THC. It only tests for an inactive "metabolite" or breakdown product of
THC. Even without physical evidence of impairment, inactive metabolites can
be present for weeks to months after consuming cannabis. Less frequent
users clear cannabis metabolites from their urine faster than regular
users. The US Department of Transportation says, "While a positive urine
test is solid proof of drug use within the last few days, it cannot be used
by itself to prove behavioral impairment . . .". Here, even the federal
government agrees urine drug testing does not prove impairment.
Fact: There is no significant impairment beyond four hours after smoking
herbal marijuana. Even the flight simulator data, often tortured by
prohibitionists to yield whatever results they wish, can be summarized.
Five flight simulator data studies between 1976 and 1991 yield mixed results
usually showing impairment up to 4 hours but no significant impairment at 8
hours or longer after cannabis consumption.
If the flight simulator testing machines are made difficult enough, then at
least one researcher, Dr. Leirer, demonstrated what he called a carry-over
or "hangover" effect up to 24 hours later. Such a hangover effect is also
seen with commonly used medicines or alcohol. The purported hangover effect
is described by Leirer as "very marginal" and is only detected in tests of
"very complex human/machine performance". Comparable, subtle effects are
reported at very low blood alcohol levels of 0.025% ( 25 milligrams of
alcohol per 100 milliliters of blood ). Even if a hangover effect can be
measured by a researcher in persons using alcohol, marijuana, or
prescription drugs 24 hours after ingestion of a drug, our laws for alcohol
do not consider 0.025% significant impairment. This alleged hangover effect
causes less impairment than the 0.04% level considered the safe level for
commercial motor vehicle drivers and far less than 0.08%, the standard
threshold for drunk driving. In other words, flight simulator data actually
demonstrate smoked cannabis beyond 4 hours causes no significant impairment
by currently accepted medical-legal standards.
In light of confusing computer flight simulation data, other researchers
study real motor vehicle accidents. In 2002, authors Gregory Chesher and
Marie Longo concluded, "At the present time, the evidence to suggest an
involvement of cannabis in road crashes is scientifically unproven".
However they note this may only reflect the evolving science since testing
for inactive urine metabolites does not prove impairment.
Because urine metabolites do not indicate impairment, some scientists
measure the parent drug responsible for impairment. Dr. Drummer measured
blood THC levels in fatal crashes in Australia and noticed an association
between high THC levels and risk of traffic fatality even in the absence of
other drugs. Using forensic evidence he determined whether a driver is
"culpable" or responsible for the fatal accident and correlated it to blood
THC levels. Drummer and colleagues conclude, "Recent use of cannabis may
increase crash risk, whereas past use of cannabis does not".
Even if one supports using parent drug blood THC levels as a marker for
impairment, it remains unclear how to define the gray area about what is
"recent" versus "past" use of cannabis. This is because the THC level below
which there is no impairment varies dramatically among individuals. Plus,
the actual numbers of persons who have only THC in the blood and are
involved in accidents is low so current studies lack the statistical
significance necessary to draw firm conclusions.
Since no culpability for fatal automobile crashes exists below blood levels
of 10 nanograms per milliliter ( ng/ml ), those concerned about legislation
suggest that any proposed thresholds be above 10 ng/ml of blood THC. For
more information about legislative considerations see: You Are Going
Directly To Jail: DUID Legislation: What It Means, Who's Behind It, and
Strategies to Prevent It by Paul Armentano:
http://www.norml.org/index.cfm?Group_IDd92
A study using coordination testing showed inevitable failure on field
sobriety testing if blood THC levels were 25 to 30 ng/ml. But, many failed
testing at 90 and 150 minutes after smoking even though plasma
concentrations were rather low. The researchers had the foresight to
conclude that "establishing a clear relation between THC plasma
concentrations and clinical impairment will be much more difficult than for
alcohol". This is because alcohol and THC are chemically different and are
metabolized differently inside the body.
With medical marijuana laws, we need research to show if there is a
correlation between clinical impairment and blood THC levels. Daily
cannabis users ( like patients ) can have levels as high as 6 to 10 ng/ml
without clinical impairment even after 24 or more hours of abstinence. Most
experts think it is premature to make firm conclusions about the proper
threshold of blood THC as a marker for "Driving Under the Influence".
Summary
There is no scientific evidence showing significant impairment beyond four
hours from smoking marijuana. There is no scientific evidence of increased
risk of motor vehicle accidents beyond four hours after smoking marijuana.
No physician would routinely condone medical use of cannabis or other
sedating drugs at work. But, careful consideration of the recommendations
in the Marinol package insert for synthetic THC preserves safety and would
be consistent with medical treatment plans for other medicines that can
impair. We have FDA-approved guidelines for synthetic THC and we should use
these same guidelines for herbal THC.
Registration in the Oregon Medical Marijuana Program should never be sole
cause for termination of employment. Medical use of marijuana within Oregon
law should be treated like medical Marinol, medical morphine, and other
medications, both in and out of the workplace. It is discriminatory to fire
an unimpaired worker whose only cause for job termination is registration
with the Oregon Department of Human Services Oregon Medical Marijuana
Program. Let us hope that we won't see the sequel of House Bill 2693
surface in the Oregon legislature next session, and if we do, let us work to
defeat such misguided and damaging public policy.
Pubdate: Wed, 05 Oct 2005
Source: Alternatives (Eugene, OR)
Issue: Fall, 2005
Column: Physicians' Perspective
Copyright: 2005 Get Real Inc.
Contact: editor@alternativesmagazine.com
Website: http://www.alternativesmagazine.com/
Details: http://www.mapinc.org/media/1149
Author: Rick Bayer
Note: Richard "Rick" Bayer, MD is board-certified in internal medicine, a
Fellow in the American College of Physicians (FACP), and practiced in Lake
Oswego for many years. He is a co-author of: Is Marijuana the Right Medicine
For You?, a chief-petitioner of the Oregon Medical Marijuana Act in 1998,
and has appeared as a medical cannabis expert witness in Oregon state
courts. For additional references see: www.omma1998.org
Cited: Oregon Medical Marijuana Program
http://www.oregon.gov/DHS/ph/ommp/index.shtml
(Cannabis - Medicinal)
(Cannabis and Driving)
(Drug Testing)
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