Extract from a recent publication (Drug and Alcohol Dependence) relating to methadone dose levels and metabolism.
The study practice has been treating drug and alcohol dependent patients for 15 years (Byrne and Wodak, 1996). Patients are referred by local doctors or other drug services and at any one time up to 150 patients are treated with opioid pharmacotherapy. Most patients live or work in the area and attend the practice for supervised dispensing for which they pay a fee, others attending public or private clinics, or pharmacies, for dosing.
There is no maximum methadone dose, although doses above 200 mg/day must be approved by a committee of the New South Wales Department of Health. Mean methadone doses calculated periodically in recent years at this practice have ranged between 89 and 107 mg/day.
Patients are seen regularly by a doctor for counselling and dose review, one- to four-weekly as their stability in treatment is demonstrated, and a doctor is available to see patients whenever the clinic is open. Dose changes are made in consultation with the patient, in response to any symptoms of opiate withdrawal, mood disturbance, continuing use of illicit opioids, or other prescribed and non-prescribed substances including alcohol, benzodiazepines and cannabis.
The practice uses an enzyme immunoassay (Microgenics CEDIA®, Fremont, CA, USA) for urine toxicology, which includes a test for opiates, sensitive to 300 ng/ml of morphine/monoacetyl morphine and having similar sensitivity for metabolites of morphine (glucuronides), for codeine and a range of other opiates. In our experience, the opiate screen remains positive for up to five days after heroin use. If the opiate screen is positive, specific thin paper chromatography is performed which has a sensitivity of 300-500 ng/ml for morphine/monoacetyl morphine.
Supervised urinary drug toxicology is performed every one to four weeks depending on the patient's progress in treatment. Patients newly in treatment are tested more frequently while those patients with consistent evidence of abstinence from illicit drugs over a period of time are tested less frequently. The testing protocol is random but is varied by the doctor or dispensing nurse on duty in response to clinical indicators of drug use (such as intoxicated presentations) and prior urine toxicology results. Urine testing is encouraged but not compulsory, and patients receiving takeaway doses are seldom asked to provide urine specimens on days when they would not otherwise attend the practice. Positive urine drug screens do not lead to forced withdrawal regimens or withholding of treatment, and do not disqualify a patient from receiving take-away doses, but are indicators for more intensive supervision including more frequent urine tests. Typically several negative opiate screens are required before a patient qualifies for less frequent urine tests.
