A randomised clinical trial as proof of principle of the analgesic effectiveness of cannabinoids on post-operative pain

Can cannabis help to control pain after surgery?

What was this study about?

This trial aimed to find out whether cannabis could help to provide pain relief after surgery. Immediately after an operation, patients were given a morphine pump which they controlled, to provide them with pain relief. After the morphine was no longer needed, patients who developed pain were invited to take part in the CANPOP trial. Those who agreed to take part were divided at random into four groups:

  • Patients in the first group were given a capsule containing tetrahydrocannabinol (one of the active ingredients in cannabis)
  • People in the second group were given a capsule of cannabis extract containing the same amount of THC. The amount of tetrahydrocannabinol (THC) used was determined by an earlier piece of research, the CANPOP Dose Finding Study.
  • People in the third group were given paracetamol
  • People in the fourth group were given a placebo

Pain relief was then assessed over the next six hours.

What difference did this study make?

CANPOP was closed because recruitment to the trial was too slow.

Type of study

Randomised trial

Contact details

Who funded the study?

The Medical Research Council.

When did it take place?

This trial began recruiting people in 2003. It closed in the same year.

Who was included?

Only 6 patients were recruited to take part in this trial. The target was 400 people.