Conversion of Chronic Pain Patients from FullOpioid Agonists to Sublingual Buprenorphine

Background: Sublingual buprenorphine-naloxone (buprenorphine SL) is a preparation that is used to treatopioid dependence. In addition, the Drug Enforcement Administration (DEA) has acknowledged the legalityof an off-label use to treat pain with a sublingual buprenorphine preparation. Buprenorphine SL is uniqueamong the opioid class of analgesics; this compound has a high affinity for the mu-receptor, yet only partiallyactivates it. Thus, buprenorphine SL can provide analgesia, yet minimize opioid side effects. Many patientson high doses of traditional opioid medication develop tolerance. Despite escalating medication dosage,a subset of patients had a paradoxical increase in pain, which has been characterized as opioid-inducedhyperalgesia (OIH). Buprenorphine SL, on the other hand, may even be anti-hyperalgesic and may have utilityin treating these challenging patients.Objective: To determine the effectiveness of converting patients from traditional full agonist opioidmedication to sublingual buprenorphine, as well as to identify patient groups that are most likely to benefitfrom this therapy. Patients who underwent conversion either had developed tolerance with diminishedanalgesia or were experiencing side effects on their opioid medications.Study Design: An observational report of outcomes assessment.Setting: An interventional pain management practice setting in the United States.Methods: Retrospective data from clinical records was compiled on 104 de-identified chronic pain patientswhose personal information had been redacted (60 men and 44 women, aged 21-78) and who had previouslybeen treated with opioid-agonist drugs; they were converted to buprenorphine SL in tablet form during thestudy. Chronic pain was defined as persistent pain for at least 6 months. Data collected from patient profilesincluded age, sex, diagnosis, medication history, pre-induction opioid intake, reason for detoxification, preinduction Clinical Opiate Withdrawal Score (COWS), and if applicable, cause of buprenorphine SL cessation.Pain levels and Quality of Life scores were recorded before and after conversion to buprenorphine SL.Outcome Measures: Level of analgesia for patients who continued conversion to sublingual buprenorphinefor more than 2 months.Results: After initiation of buprenorphine SL therapy for more than 2 months, the mean pain scores on ascale from 0-10 decreased by 2.3 points (P < 0.001). Patient Quality of Life (QoL scale) was not significantlyaffected by buprenorphine SL therapy (P = 0.14). The success rate was highest for patients using morphine,oxycodone, and fentanyl before buprenorphine SL induction. These patient groups had a 3.7 point decreasein pain for those taking morphine, a 2.5 point decrease in pain for those taking oxycodone, and a 2.2point decrease for those taking fentanyl. The smallest pain reduction was seen in the patient group usingoxymorphone before conversion with a 1.1 point decrease in pain. Patients taking between 100-199 mgmorphine equivalent per day experienced the greatest reduction (2.7 points) in pain scores. Patients takingbetween 200 and 299 mg morphine equivalent before buprenorphine SL induction exhibited a decrease ofover 2 points on average. Patients taking > 400mg morphine equivalent reported the smallest reduction inpain scores, on average a 1.1 point decrease.Limitations: This study is limited by its observational nature.Conclusions: Patients continuing buprenorphine SL therapy for more than 60 days reported significantdecreases in pain (2.3 points). Patients on doses of opioid medication between 100-199 mg morphineequivalents seemed to fare better with conversion to buprenorphine SL than patients on the highest doses(> 400 mg morphine equivalents). The opioid drug used by the patient before buprenorphine SL inductionappears to have some effect on buprenorphine SL conversion success. Patients previously taking morphine,oxycodone, and fentanyl had the greatest decrease in pain after conversion to buprenorphine SL.Key Words: Sublingual buprenorphine-naloxone, buprenorphine, buprenorphine SL, opioid dependence,opioid conversion, opioid-induced hyperalgesia, analgesia, full agonist opioids, opioid tolerance.