The duration and course of opioid therapy in patients with chronic non-malignant pain

Background: Prescription databases provide the opportunity for investigating opioid treatment and co-medication within large populations. So far, few studies have investigated the duration of opioid therapy, and large differences in discontinuation rates have been reported. Methods: Data from the Norwegian Prescription Database were used to follow the study population of all adult persistent opioid users with non-malignant pain in Norway in 2005 (n = 44,867) for 6 years. Persistent opioid use was defined as being dispensed = 180 defined daily doses (DDD) or 4500 mg oral morphine equivalents (OMEQ) during a 365-day period. The study population was stratified according to previous opioid use into new persistent opioid users, without previous persistent opioid use, and previous low-dose or previous high-dose persistent opioid users, having earlier persistent opioid use and received less or more than 120 mg OMEQ/day in 2005, respectively. Results: Twenty-seven percent of new, 59% of previous low-dose, and 55% of previous high-dose users met the criteria of persistent use of opioids each year. Exactly, 22%, 11%, and 3% increased their cumulative yearly opioid dose by 200% or more during the study period. With 80% still being regular users of either drugs, 6 years later, long-term persistent opioid users were more likely to continue concomitant use of benzodiazepines or z-hypnotics than other users, Conclusion: The findings confirm high discontinuation rates in patients receiving opioids for chronic non-malignant pain. However, a clinically significant number of patients increase their doses over 6 years and many patients combine long-term opioid treatment with benzodiazepines and z-hypnotics.