30 chronic pain patients who were on stable doses of opioids received a single dose of each of10 mg of dronabinol (a synthetic cannabinoid), 20 mg dronabinol, or placebo in a random order, followed by 4 weeks of 5-60 mg dronabinol (open-label). The primary outcome was total pain relief at 8 hours in the randomized phase and change in pain intensity on a numeric rating scale (NRS) in the open-label phase. Secondary outcomes included patient satisfaction, side effects, dropouts, pain bothersomeness, mood, evoked pain, and plasma levels of THC. Dronabinol reduced pain intensity and improved satisfaction among patients with chronic non-cancer pain when added to standard opioid therapy.