Marijuana (Cannabinoids)Pain

Do cannabinoids improve opioid analgesia?

Cannabinoids and opioids share several pharmacologic properties and may act synergistically. But, the potential pharmacokinetics and safety of the combination in humans are unknown.

Researchers at the University of California at San Francisco attempted to answer these questions.

First, the details.

  • 21 people with chronic pain and treated with sustained-release morphine or oxycodone (OxyContin) twice daily participated in a 5-day inpatient study.
  • Participants inhaled vaporized cannabis (900 mg) in the evening of day 1, 3 times a day on days 2 to 4, and in the morning of day 5.
  • Blood samples were taken at 12-hour intervals on days 1 and 5.
  • The extent of chronic pain was assessed daily.

And, the results.

  • The bioavailability for either morphine or oxycodone did not change after exposure to cannabis.
  • Pain was significantly decreased an average of 27% after the addition of vaporized cannabis.

The bottom line?

The authors concluded, “Vaporized cannabis augments the analgesic effects of opioids without significantly altering plasma opioid levels. The combination may allow for opioid treatment at lower doses with fewer side effects.”

In an editorial, Dr. Mark Ware at McGill University cautions that before changing normal practice in pain management everyone should consider that it was a small study. Also, the dose might have been 900 mg, but the duration of exposure wasn’t reported and the instructions given to the participants were vague (inhale as much as possible). There was no control group for comparison, and we don’t know how many of the participants got stoned, making their response suspect.

The most important finding may be that a vaporizer is a viable alternative to smoking weed. Combining the vaporizer with a metered dose system might be useful. But, that’s for another study.

12/18/11 21:01 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.