Feasability and safety of transfer from racemic methadone to (R)-methadone in primary care: clinical results from an open study.

Methadone is a proven first-line treatment in opioid dependence but few studies have addressed the efficacy of different isoforms of methadone or the transfer from one form to the other. This was a 4-week open study to examine the feasibility and safety of transfer from racemic methadone to (R)-methadone in primary care patients. A total of 1552 opioid-dependent patients formerly treated with racemic methadone were included and followed for 4 weeks after transfer to (R)-methadone. There were few drop-outs, and 1426 patients (91.9%) completed the 4-week transfer period. There were few adverse events or side effects and no deaths occurred during treatment. The number of drug-positive urine screens decreased from 61.2 to 39.8%. Withdrawal symptoms, craving and compliance improved significantly after transfer to (R)-methadone. We conclude that transfer from racemic to (R)-methadone is a safe and practical procedure.