Study to Evaluate the Efficacy of Dronabinol (Marinol) as Add-On Therapy for Patients on Opioids for Chronic Pain

The purpose of this research study is to determine if Marinol alleviates pain in patients with chronic pain who are currently taking opioids. The study begins with a 2-hour initial visit followed by three 8-hour appointments at Brigham and Women's Hospital. At each 8-hour visit, patients receive a dose of medication and complete surveys relating to pain. During the first visit a brief examination and a few surveys about pain, quality of life, and medical history are given. The study doctor then determines if the participant continues to qualify for the study. If qualified for the study, patients receive a daily diary to record pain levels and pain medications; this will take about 5 minutes each day. After completion of the diary, patients begin the 8-hour visits. Patients visit the Pain Trials Center three times to receive study medication. After taking the study medication, participants remain in the clinic for 8 hours to complete hourly surveys about pain and pain relief. Subsequent to these visits, patients may enter a 1-month extension where Marinol is taken at home, and pain levels are recorded in a diary. Participants can change the dose of study drug to better control pain and side effects, after speaking with study staff. The study then concludes with a final 30-minute visit to summarize the participant's experience in the clinical trial.