Perhaps
the
biggest
challenge
in
understanding marijuana stems from the fact
that it is not a bespoke drug designed to act in
a specific way on the body — it's a complex
plant that appears to provide a wealth of
health benefits.
The cannabis sativa plant contains more than
85 cannabinoids, a variety of chemical
compounds that also exist in the body. Just as
opioid pills activate the opioid receptors (and
limit a person’s perception of pain),
cannabinoids in marijuana activate the
cannabinoid receptors, located throughout the
body, including in the brain, liver and immune
system.
To date, we really know about only two of
these cannabinoids: tetrahydrocannabinol and
cannabidiol. Research into THC and CBD has
led to the development of drugs such as
dronabinol (Marinol), a synthetic cannabinoid
approved by the U.S. Food and Drug
Administration for nausea and vomiting from
chemotherapy and as an appetite stimulant,
anti-nausea and anti-pain medication for
AIDS patients. Nabiximols (Sativex), another
cannabinoid drug, is THC and CBD that is
derived from the plant and delivered as a
mouth spray.
It’s available in Europe and several other
countries—but not yet FDA-approved—for
multiple sclerosis patients to treat
neurological pain and spasticity.
One study on nabiximols for the treatment of
cancer-related pain produced disappointing
results.
However, the GW Pharmaceutical Company,
the maker of Sativex, is pushing through with
further trials to evaluate the drug as a potential
adjunctive therapy for opioids for pain
management in patients with advanced
cancer.
But how other cannabinoids work together is
still much of mystery, says Dr. David
Casarett, a professor of medicine at the
University of Pennsylvania’s Perelman
School of Medicine and the author of Stoned:
A Doctor’s Case for Medical Marijuana.
This means researchers aren’t entirely sure
why the plant could help people manage
symptoms like nausea and pain. “Marijuana is
not as much of a science as it should be,” he
says.
In large part, says Casarett, that’s because
medical marijuana has proved to be most
effective in palliative care, the medical
specialty that focuses on managing symptoms
of disease and improving a patient’s quality of
life—and there is very little funding for
palliative care in this country. “That's
changing slowly,” he says, “but it's still much
easier to get funding to test disease-modifying
treatments than it is to develop and test
palliative therapies, including cannabis.”
We are starting to get some idea of the
palliative power of cannabis, Abrams says.
“The reason we think we have this whole
pathway of the receptors and the
endocannabinoids is to get us to forget things,
and particularly to get us to forget pain,”
he says. In addition, cannabinoids relieve
symptoms of nausea because that’s also a
physiological reaction stemming from the
central nervous system.
With the public perception of marijuana
changing rapidly, barriers to studying the
plant’s medicinal potential are beginning to
fall. Earlier this spring, for example, the
Obama administration announced it would
remove some of the restrictions on medical
marijuana research. In the meantime, though,
it is clear that marijuana has a unique and
important role to play in cancer care.
“People are realising that even when patients
do well in terms of survival, there’s a lot of
suffering along the way that needs to be
addressed,” says Casarett. “For many
patients, [marijuana] is an opportunity to take
control over their disease and symptom
management when they can't get the relief,
they need from the health care system.”