THE SCIENCE OF POT

Pain Relief May Be Just the Beginning of the Potential Contained In
Medical Marijuana, Reports Sharon Kirkey, Postmedia News

After all the usual and proper medical approaches did nothing for her
pain, Cheryl Campbell, a nurse and mother, says she finally built up
the courage to ask her doctor, "How do you feel about prescribing me
marijuana?"

The 30-year-old Ottawa woman suffers from fibromyalgia and chronic
fatigue syndrome. Her pain is body-wide - a constant, sometimes
stabbing ache in her back, hips, knees, shoulders and virtually every
joint. Doctors once put her on morphine. It cut the pain, but she
couldn't function. She says her mind felt so heavy with fog she
couldn't carry on a conversation.

She's been using marijuana for pain for two years; she has a federal
licence to possess it. She says it helps her sleep at night. In the
morning, it helps ease the stiffness in her hips and back enough that
she can make it into the shower.

Campbell says she owes her ability to get through each day to a drug
that critics condemn, especially when it's smoked - which is how most
of the thousands of Canadians who self-medicate with pot prefer to
take it.

The U.S. Drug Enforcement Adminstration was unequivocal this year:
Smoked marijuana is not medicine, and it's not safe.

"No matter what medical condition has been studied," the agency ruled,
"other drugs already approved by the (U.S. Food and Drug
Administration) have been proven to be safer than smoked marijuana."

But research into medicinal marijuana is undergoing a surge of
interest, with more evidence emerging not only of its ability to ease
human suffering, but also of its apparent safety.

Some say cannabis may be less toxic to humans than over-the-counter
pain relievers.

Four small but scientifically controlled experiments in recent years
have concluded that smoked cannabis can provide moderate relief from
chronic, severe non-cancer pain - including HIV-related nerve pain and
post-traumatic neuropathy, a dreaded condition that can follow an
injury or medical procedure. Both are notoriously resistant to
conventional treatments.

Scientists are only beginning to tease out the possible anti-cancer
properties of pot. Early experiments in animals suggest that purified
forms of THC and cannabidiol - two major constituents of marijuana -
can induce certain cancer cells, including breast cancer cells, to
essentially kill themselves off - a process known as apoptosis. The
cells self-destruct; they stop dividing and spreading. Cannabinoids
also seems to shut down a tumour's lifegiving blood supply.

Meanwhile, researchers across Canada are testing cannabinoids against
arthritis, glaucoma and gastrointestinal inflammatory diseases, such
as Crohn's.

"Science is just scratching the surface," says Dr. Mark Ware, head of
the Canadian Consortium for the Investigation of Cannabinoids and
director of clinical research at the Alan Edwards Pain Management Unit
at Montreal's McGill University Health Centre.

In Canada, synthetic versions of THC and other pure cannabinoids are
already available by prescription - pills and sprays approved for
cancer pain, for nausea associated with chemotherapy, to stimulate
appetite and for the relief of the pain and spasticity of multiple
sclerosis.

Medical marijuana, Ware argues, is essentially just a different
delivery system for cannabinoids.

It's crude, he acknowledges. It's also associated with potential harms
through the sheer act of burning the plant and smoking it. But even
then, he says, the evidence is uncertain.

"It's not a done deal that smoking cannabis alone is as potent a
cancer-causing agent as tobacco," Ware says.

According to U.S. drug enforcement officials, while smoked marijuana
can cause changes in lung tissue that may very well unleash cancer,
"it's not possible to directly link pot use to lung cancer based on
existing evidence."

But does it have any legitimate role in medicine?

Cannabis sativa preparations have been used as medicine for thousands
of years. In The Science of Marijuana, retired Oxford University
professor Les Iversen, chair of the U.K. government's Advisory Council
on the Misuse of Drugs, says Chinese herbal medicine texts dating to
2800 BC recommended cannabis for constipation, gout, malaria,
rheumatism and menstrual complaints.

Modern interest in cannabis exploded in the 1980s when researchers
discovered all mammals - notably humans - have an endogenous, or
built-in, cannabinoid system. Essentially, we make our own marijuana.

Two types of receptors for cannabinoids - CB1 and CB2 - are found in
the brain and spinal cord, nerve cells and immune tissues. The body
produces a natural, THC-like chemical called anandamide, the socalled
"bliss chemical," that binds to these receptors.

Anandamide has been found to play a part in pain, anxiety and
depression.

We don't walk around high all the time because anandamide is released
in response to noxious or painful stimuli, such as an injury or
inflammation. The neuro transmitter latches onto the receptors and, in
the case of pain, helps settle down the firing of nerves in the pain
pathway. But it's broken down quickly, chewed up by enzymes so rapidly
that it never reaches a level sufficient enough to cause a high.

When someone smokes marijuana, those exogenous cannabinoids "are
obviously going to hit all the cannabinoid receptors in the body,"
explains Dr. Jason McDougall, associate professor in the departments
of pharmacology and anesthesia at Dalhousie University in Halifax.

Since one of those receptors, CB1, is most prominent in the brain,
"That's why we get a lot of those psychoactive effects of the drug."

But the cannabinoids in pot also occupy receptors in the peripheral
nerves involved in the body's pain system, as well as nerves
controlling movement and other functions.

Studies of patients with multiple sclerosis have found that cannabis
can help with muscle pain, tremors and depression; patients have
reported feeling better able to move.

Laboratories around the world are examining ways to harness this
potential in a way that minimizes psychotropic side-effects. Some are
trying to develop a drug that acts peripherally; others are looking
for drugs that block the rapid breakdown of our own endogenous
cannabinoids - "the same way we treat depression by giving
antidepressants that can inhibit or interfere with the breakdown of
certain chemicals in our brain, like serotonin," says Dr. Mary Lynch,
director of the pain management unit at Queen Elizabeth II Health
Sciences Centre in Halifax and past president of the Canadian Pain
Society.

Despite its widespread illegal use, there are few, "if any," reports
of fatal overdoses from cannabis, Iversen said. By contrast, thousands
die each year from "catastrophic" bleeding in the gut caused by
non-steroidal anti-inflammatory drugs, he said.

Doctors say what makes cannabinoids safer than opioid pain medications
is that cannabinoid receptors, unlike receptors for opioids, aren't
present in high numbers in the brain stem regions that control
breathing and heart rate.

"This is one of the reasons cannabinoids are generally safer than many
of the other drugs used to treat human disease and pain," Lynch says.

The most common side effects are sedation and foggy thinking. "You can
also get high," Lynch says.

"But many of our patients adjust the dose so they can avoid the
side-effects and aim for the therapeutic effects, similar to the way
we use any drug."

Ware said for cases of severe intractable pain, oral cannabinoids
often don't work. Some patients prefer the inhaled mode because it's
the fastest for pain relief.

McDougall of Dalhousie has found that when synthetic cannabinoids are
injected into the joints of arthritic rats, "we can control the pain
in the joint itself" while avoiding the psychoactive effects of the
compounds.

"We don't have great agents now," he says. Many drugs used for
arthritis have "multiple negative sideeffects," he says - including a
potential increased risk for cardiovascular disease, kidney disease
and gastro-intestinal bleeding associated with long-term use of
non-steroidal antiinflammatory drugs.

"There are still a lot of arthritis patients out there who are not
getting adequate pain relief for their disease," he said. Many are
turning to pot.

That makes Dr. Meldon Kahan nervous. He and others worry that smoked
marijuana's promotion as a legitimate medicine, especially for pain,
is driving a rise in illicit use when Canadians are already among the
highest per capita users of pot in the western world.

"A lot of people - particularly young people - are harmed by the
notion that cannabis is this harmless herb," says Kahan, a physician
and associate professor in the department of family medicine at the
University of Toronto. He says cannabis may trigger psychosis in
people with a genetic vulnerability and more users - young and old -
are becoming addicted.

For select conditions such as HIV-related neuropathy, cannabis "may
very well have benefit," says Kahan, formerly of the Centre for
Addiction and Mental Health in Toronto.

"Cannabis, especially daily use, makes people feel relaxed. It reduces
anxiety and stress. People feel mellow and so they may perceive their
pain as being blunted, or milder."

Despite the polarizing nature of pot, "we have to take the middle
ground and say, 'Where are the potential benefits?' " Ware says.

[sidebar]

Medicinal marijuana pros & cons

Pro:

May offer pain relief from chronic neuropathic pain - pain caused by
accidental or surgical injury to nerves

- - Effective for HIV related pain and an appetite stimulant for people
living with AIDS

- - May provide relief for painful muscle spasms from multiple
sclerosis

May reduce opioid dose in treatment of chronic, non-cancer
pain

- - Cannabis smoking by itself does not appear to be a major risk factor
for head, neck or lung cancer

- - Can improve mood and sleep in patients with chronic
pain

Cons

Can cause drowsiness, dry mouth, headache; can impair psychomotor
skills

Increased risk of heart attack within one hour of use

- - May trigger psychosis in those who are vulnerable due to personal or
family history

- - Can cause changes in lung tissue with longterm use that may lead to
cancer

- - Possible increased risk of cardiovascular disease

- - Little known about long-term safety concerns