Prescription opioid misuse has recently become a highly prevalent problem in the United States. In 2007, there were 2.5 million new users of prescription medications for non-medical purposes among individuals aged 12 years or older in the United States; 2.15 million people were new users of prescription opioid drugs.1
Among users of all illicit substances, this group represented the largest number of past-year initiates in 2007.
With the increased prevalence of prescription opioid misuse, studying treatments for those who develop dependence on prescription opioids is critical. Most treatment studies of opioid-dependent populations have heretofore focused either exclusively or predominantly on heroin users.2–5
However, some evidence suggests that traditional treatments for opioid dependence may result in differential outcomes for persons dependent upon heroin versus prescription opioids.6,7
Therefore, studying treatment outcomes in a population of exclusively prescription opioid-dependent individuals is necessary to determine whether specific treatment strategies should be tailored for this population.
To this end, the multi-site Prescription Opioid Addiction Treatment Study (POATS) is currently being conducted under the auspices of the National Institute on Drug Abuse (NIDA) Clinical Trials Network (CTN); the CTN, a partnership between academic research centers and community drug abuse treatment programs, conducts multi-site clinical trials with drug-dependent patients in community treatment programs. POATS was launched in 2006 in response to the epidemiologic trends described above; this study is comparing the efficacy of different durations and intensities of combinations of buprenorphine/naloxone and drug counseling in the treatment of patients with prescription opioid dependence.
In designing this study, one of the key methodological issues that we faced involved defining our study population. When doing so, two specific populations presented the greatest challenge when determining eligibility criteria: 1) those who had used heroin, and 2) individuals with pain. In both instances, a goal was to identify a distinct but generalizable population of treatment-seeking individuals who were dependent upon prescription opioid drugs. We sought to distinguish our population from those who had participated in previous studies (i.e., those who had primarily used heroin). However, because some individuals who are dependent upon prescription opioids have also used heroin,8
we did not want to be so strict in our exclusion criteria regarding heroin use as to end up recruiting a study population that was unrepresentative of patients seeking treatment for prescription opioid dependence in clinical settings. We also recognized that patients who had been prescribed opioids for pain and had become dependent on them could differ substantially from individuals without pain who used prescription opioids illicitly.9
In deciding which of these potential participants to include in our study, then, our goal was to identify a population that was 1) distinct, 2) generalizable to the general population of those dependent on prescription opioid drugs (thus making our results applicable to patients seeking treatment outside of research settings and allowing us to recruit an adequate number of participants to conduct our study successfully), and 3) heterogeneous enough to determine whether different subtypes would respond to treatment differentially. Because other studies of individuals dependent upon prescription opioids will be conducted, this manuscript will review the various methodological issues we faced in defining our population. We will review our decisions and discuss the results of those decisions in relation to 1) our ability to recruit an adequate participant population, and 2) the types of potential participants that we excluded.