The study is to primarily measure safety and interactions between oral doses of Naltrexone/Bupropion and i.v. Methamphetamine.

Inclusion Criteria:

• Are MA experienced but not dependent, males or females aged 21-to-50 years.
• Reported use of MA during the past six months without experiencing an adverse consequence plus a life time MA or amphetamine use history of at least four occasions of use.
• Have a body mass index (BMI) between 18 and 30.
• Are willing and able to give written consent.
• Are not currently a subject (including still in the follow-up period) of another drug research study.
• Have no medical contraindications determined by the following: an adequate medical history, a physical examination including vital signs, 12-lead ECG, hematology, blood chemistry, and urinalysis.
• Have a negative drug test for barbiturates, benzodiazepines, opiates, cocaine, amphetamines and ethanol at the time of hospital admission (Day 0).
• Are females who have a negative pregnancy test at hospital admission.
• Are of either non-childbearing (tubal ligation or total hysterectomy) or of childbearing potential using one or more of the following barrier methods of contraception: male or female condoms (with/without spermicide), diaphragm (with spermicide) and/or copper containing intrauterine device (with/without spermicide). No other contraceptives are acceptable.

Exclusion Criteria:

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