Impulsivity and Stimulant Administration

Inclusion Criteria:

1. age 18 - 50 years,

2. voluntary, written, informed consent,

3. physically healthy by medical history, physical, neurological, ECG, and laboratory
examinations,

4. DSM-IV criteria for Cocaine Abuse (305.60) or Cocaine Dependence (304.20)

5. recent street cocaine use in excess of amounts to be administered in the current
study,

6. intravenous and/or smoked (crack/ freebase) use,

7. positive urine toxicology screen for cocaine,

8. for females, non-lactating, no longer of child-bearing potential (or agree to practice
effective contraception during the study), and a negative serum pregnancy (β-HCG)
test.

Exclusion Criteria:

1. Other drug dependence (except nicotine) as determined by urine toxicology or interview

2. < 1 year of cocaine dependence,

3. a primary major DSM-IV psychiatric diagnosis (schizophrenia, bipolar disorder, etc.),
unrelated to cocaine,

4. a history of significant medical (cardiovascular) or neurological illness, ie prior
myocardial infarction, current active symptoms of cardiovascular disease / angina,
evidence of cocaine-related cardiovascular symptoms, prior arrhythmias or need for
cardiovascular resuscitation, neurovascular events such as transient ischemic attacks,
stroke, and/or seizures Parameters re: elevations in vital signs are now explicitly
specified under "Safety features built into our one-day self-administration paradigm).

5. current use of psychotropic and/or potentially psychoactive prescription medication,

6. seeking treatment for drug abuse/dependence (for experimental cocaine component),

7. physical or laboratory (β-HCG) evidence of pregnancy.

8. current use of any medication (prescription or over-the-counter) determined to cause
potential drug interactions by the study physicians.