Switching between Methadone and Morphine for Maintenance Treatment of Opioid Dependence: Impact on Pain Sensitivity and Mood Status

Methadone maintenance is associated with hyperalgesia and elevated mood disturbance-effects opposite to those induced by acute opioid administration, which may undermine outcomes during substitution therapy. This study examined the impact of switching between methadone and slow-release morphine on pain sensitivity and mood status in 14 methadone maintenance patients using an open-label crossover design. Pain responses were nearly identical for each drug. Patients reporting inadequate withdrawal suppression on methadone showed greater mood stability when transferred to morphine, but overall mood disturbance levels did not differ between drugs. Hyperalgesia and mood disturbance cannot be resolved by changing from methadone to morphine maintenance.