Dose Response of Mirtazapine to Methamphetamine Induced Interest, Mood Elevation and Reward

The primary purpose of this study is to determine if Mirtazapine will produce a decrease in interest in the drug, a decrease in mood elevation, and/or a decrease in reward when given before methamphetamine compared to placebo. Participants will be screened with a psychiatric interview, medical history and physical, laboratory tests, drug of abuse screen and, if female, a urine pregnancy test. They will be provided written informed consent. They will be studied in a within-subjects examination of the subjective mood responses of mirtazapine and methamphetamine. Interactions between methamphetamine and mirtazapine will be assessed by pharmacokinetic studies. Each participant will be introduced to rating scales and cognitive tasks described below. Participants will remain in the research unit for 5 hours on each day that they receive study medication or placebo. They will spend five days in total on the research unit, one day separated by at least one day; then in two day blocks separated by at least one day from another two day block. A venous catheter will be placed for blood draws. Blood pressures and heart rates will be recorded and assessed. Participants will be randomized and double blinded to receive either placebo or mirtazapine orally two hours prior to the administration of randomized and double blinded methamphetamine or placebo in order to have the peak effects of the drugs overlap. VAS-mood, ARCI, GRS, POMS and POMS-E, neurocognitive tasks Trails A and B and Symbol digits modalities test will be administered prior to the mirtazapine or placebo dose, and repeated after the administration of methamphetamine or placebo. After the administration of methamphetamine or placebo, vital signs will be assessed every 15 minutes and the measures will be repeated until 120 minutes have passed from the initial dose of methamphetamine or placebo. Blood will be drawn at one, three and four hour marks for pharmacokinetic testing. This will be repeated on each testing day.