Effect of pot smoking on pain all in the dose: study

By David Douglas

NEW YORK (Reuters Health) - A study suggests that smoking a moderate amount of cannabis (marijuana) may relieve pain but smoking high doses may increase pain.

"Previous studies have suggested that smoked cannabis increases pain," lead investigator Dr. Mark Wallace of the University of California, San Diego told Reuters Health. "This is the first study using a dose-response method that suggests smoked cannabis has a therapeutic window with moderate doses decreasing pain and high doses increasing pain."

In a group of healthy volunteers, Wallace and colleagues studied the effect of low, medium and high doses of smoked cannabis or placebo on pain induced by injecting capsaicin into the forearm 5 and 45 minutes after drug exposure.

No dose of cannabis had any effect at 5 minutes, but by 45 minutes after exposure there was a significant decrease in pain with the medium dose and a significant increase in pain with the high dose. No such effect was seen with the low dose.

Despite their findings, the researchers emphasize that no conclusions on the pain-relieving efficacy of smoked cannabis can be made from this study. Further study is needed, they conclude.

SOURCE: Anesthesiology November 2007.