Dextromethorphan, Memantine Monotherapy, or Combined Use of Dextromethorphan and Memantine in Amphetamine Addiction

The investigators will conducted a randomized double-blind placebo-controlled study to investigate the treatment outcomes of add-on low dose dextromethorphan (60mg/day, DM), memantine (5 mg/day, MM), or dextromethorphan (60mg/day) and memantine (5mg/day) combination (DM+MM) in amphetamine-type stimulants use disorder patients. The investigators will recruit 120 patients with ATSUD in three years and allocate participants to add-on DM, MM, DM+MM or placebo group in a 1:1:1:1 ratio (participants will also undergo usual psychosocial interventions).The investigators will follow up the participants for 12 weeks and measure the treatment responses, urine drug tests, craving scales and side effects to evaluate the therapeutic effects of add-on DM, MM, or DM+MM. Neuropsychological assessments, tests for inflammatory parameters and neurotrophic factors, and brain functional magnetic resonance imaging (fMRI) will also be evaluated during 12-weeks follow up.