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Higher marijuana intake increases
pain
28 October, 2007
Though smoking marijuana, or
cannabis, in moderate doses helps
reduce pain, the pain increases at
high doses.
A new study, published in the latest
issue of the journal Anesthesiology,
stresses that marijuana reduces pain
only within a smaller dose range.
Dr Mark S Wallace, of the University
of California, San Diego, the United
States, and lead author of the study,
said that the study suggests that
there is a therapeutic window for
analgesia, with low doses being
ineffective, medium doses resulting in
pain relief and high doses increasing
pain.
Dr Wallace and colleagues assessed the
effects of smoking marijuana on pain
responses in 15 healthy volunteers. On
different days, the research subjects
smoked low, medium, or high doses of
cannabis (based on the content of
9-delta-tetrahydrocannabinol, the main
active chemical in marijuana), or an
inactive placebo.
Pain was induced in the healthy
volunteers by injecting capsaicin, the
“hot” chemical found in chili peppers,
into the skin. (Capsaicin injection is
a standard technique used in pain
studies, according to the authors of
the study).
Five minutes after smoking, none of
the three doses of cannabis had any
effect on pain responses to capsaicin.
However, 45 minutes after smoking the
moderate dose of cannabis, pain was
significantly reduced – about 6 points
lower on a 100-point scale, compared
with the inactive placebo.
In contrast, 45 minutes after smoking
the high dose of cannabis, pain scores
were increased – about 8 points higher
than with placebo.
The low dose of cannabis was found to
have no effect on pain scores. None of
the three doses affected the spread of
pain beyond the area injected with
capsaicin.
Levels of tetrahydrocannabinol
measured in the blood were
significantly related to reduced pain
scores at the moderate dose of
cannabis, but not to the increase in
pain with high-dose cannabis. The
volunteers’ sense of feeling “high”
increased with each dose of cannabis,
even though the pain-relieving effects
did not, the study found.
According to Dr Mark S Wallace, with
several states in the United States
having passed laws legalizing the
medical use of cannabis, there has
been a call for more research on
medicinal cannabis.
Dr Wallace and colleagues have called
for further research, including
studies of the clinical value of the
pain-reducing effects of cannabis.
However, Dr Wallace added, based on
this study’s findings, he would not
recommend marijuana as a method of
pain reduction at this time.
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