Patients admitted consecutively to the in-patient treatment unit of the Clinical Research Treatment Institute of the ARF within an 11-month period (June 1990 to April 1991) with the diagnosis of severe oral opioid dependence were identified. Another study was attempting to examine the relationship between methadone and liver enzymes; therefore, all patients using codeine, oxycodone, morphine or hydrocodone were eligible to participate in both studies. After patients signed informed consent forms (as approved by the Ethics Review Board of the University of Toronto), the psychoactive substance use disorder module of the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised (DSM-III-R) was conducted by two trained investigators. Chart reviews were performed to obtain the following information: demographic characteristics such as age, sex and education; the type of asthma treatment received by these patients (eg, supportive therapy and counselling, methadone tapering or the use of other medications to minimize withdrawal or treat psychiatric comorbidity); and outcome of treatment (eg, relapse, additional treatment).
Patients with prescription opioid dependence on codeine, oxycodone, morphine or hydrocodone, according to DSM-III-R criteria, and 16 years of age or older at the time of in-patient treatment were eligible to participate in the study.
The severity of psychoactive substance use dependence according to DSM-III-R is categorized as mild, moderate, severe, or in partial or full remission. The DSM-III-R definition of severe dependence is “many symptoms in excess of those required to make the diagnosis, and the symptoms markedly interfere with occupational functioning or with usual social activities or relationships with others” . For this study, the operational definition of severe dependence was that at least seven of nine DSM-III-R criteria were met, or fewer than seven criteria but social and occupational impairment severe enough to require in-patient treatment for opioid withdrawal.
Oral opioid doses were converted to codeine equivalents to permit comparisons. Oxycodone 0.15 mg was equivalent to codeine 1 mg.