Subjects will receive placebo, then one hour later, placebo

Subjects will receive placebo, then one hour later, methamphetamine

Subjects will receive entacapone, then one hour later, placebo

Subjects will receive entacapone, then one hour later, methamphetamine

Entacapone 200 mg oral dose

Profile of Mood States is a 65 item questionnaire using a Likert rating scale to assess transient, distinct moods. The questionnaire contains 65 words/statements that describe feelings people have. The test requires you to indicate for each word or statement how you have been feeling in the past week including today. A Total Mood Disturbance score is calculated by adding scores for Tension, Depression, Anger, Fatigue and Confusion and then subtracting the Vigour score. The Total Mood Disturbance scale ranges from -32 to 200 with lower scores indicative of people with more stable mood profiles.

The subjective effects of the study drug were evaluated with the Addiction Research Center Inventory (ARCI-49), a 49 item questionnaire consisting of true/false items. True items receive a score of 1 if answer is 'True', false items receive a score of 1 if answer is 'False'. No points are given when answer is opposite to scoring direction. There are 5 subscales: Morphine Benzedrine group scale to measure euphoria (range: 0-16 with higher numbers indicating more euphoria), A Lysergic Acid Diethylamide group scale to estimate dysphoria and agitation (range: 0-14 with higher scores indicating more dysphoria), a Pentobarbital Chlorpromazine Alcohol group scale to measure sedation (range: 0-15 with higher scores indicating more sedation), and a Benzedrine group scale and an Amphetamine Scale to assess stimulant effects (range: 0-13 and 0-11, respectively, with higher scores indicating higher stimulant effects) .

The Global Rating of Stimulation is a 1-item question "I feel light-headed, restless, or speeded-up" in which the participant is asked to circle one answer on a scale from 0-4, 0 is 'normal', 1 is 'slightly', 2 is 'moderately', 3 is 'very much', and 4 is 'extremely'. Whichever number they circled is their reported score. A higher score is indicative of a greater stimulating effect.

Two computer tests were administered to measure how each medication intervention effects cognitive functioning. The tests administered included the Rapid Visual Information Processing Task (RVIPT), a 6 minute test of sustained attention in which participants are requested to detect target sequences of digits and the Digit Symbol Substitution Task (DSST), a 2 minute test of psychomotor speed and sustained attention consisting of digit-symbol pairs followed by a list of digits where the subject identifies the symbol that corresponds to each digit as fast as possible. The number of correct responses within the allowed time is measured. Higher scores on both tasks indicate better performance.

Participants who completed all four study arms including:

1. Placebo followed by Placebo
2. Placebo followed by Methamphetamine (20 mg)
3. Entacapone (200 mg) followed by Placebo
4. Entacapone (200 mg) followed by Methamphetamine (20 mg)

Profile of Mood States is a 65 item questionnaire using a Likert rating scale to assess transient, distinct moods. The questionnaire contains 65 words/statements that describe feelings people have. The test requires you to indicate for each word or statement how you have been feeling in the past week including today. A Total Mood Disturbance score is calculated by adding scores for Tension, Depression, Anger, Fatigue and Confusion and then subtracting the Vigour score. The Total Mood Disturbance scale ranges from -32 to 200 with lower scores indicative of people with more stable mood profiles.

The analysis population includes only the 12 subjects that completed each intervention of the study.

Subject will receive one dose of open-label methamphetamine 20 mg oral dose on their second visit, the familiarization visit.

One subject's blood pressure reached 180/100 after ingesting Methamphetamine 20 mg pill but was in the 160s/90s for two hours before normalizing. This subject was removed from the study after this incident.