Inclusion Criteria:

• Speaks English
• Not seeking treatment for methamphetamine dependence at study entry
• Meets DSM-IV criteria for methamphetamine abuse or dependence
• Smokes or intravenously uses methamphetamine
• Resting pulse between 50 and 90 beats per minute within 2 days prior to study entry
• Systolic blood pressure between 85 and 150 mmHg and diastolic blood pressure between 45 and 90 mmHg within 2 days prior to study entry
• Electrocardiogram demonstrating normal sinus rhythm, normal conduction, and no clinically significant arrhythmias
• Medical history and brief physical examination demonstrating no clinically significant contraindications for study participation

Exclusion Criteria:

• History or evidence of seizures or brain injury
• Previous adverse reaction to methamphetamine
• Neurological or psychiatric disorders (e.g., psychosis, bipolar illness, or major depression)
• Organic brain disease or dementia
• History of any psychiatric disorder that requires ongoing treatment or that would make study compliance difficult
• History of suicide attempts within the 3 months prior to study entry
• Heart disease or high blood pressure
• Family history of early cardiovascular morbidity or mortality
• Untreated or unstable medical illness, including neuroendocrine, autoimmune, liver, kidney, or active infectious disease
• HIV infected
• AIDS-defining illness
• Currently taking antiretroviral medication
• Pregnant or breastfeeding
• Unwilling to use an adequate method of contraception for the duration of the study
• History of respiratory illness (e.g., asthma, chronic coughing, and wheezing)
• Currently using alpha or beta agonists, theophylline, or other sympathomimetics