Eligibility Criteria:
Inclusion Criteria:
* Diagnosis of ADHD, including degree of symptomatology, as determined by a structured clinical assessment based on the DSM-IV (SCID-1); supplemented by administration of the Schedule for Affective Disorders and Schizophrenia for School-Age Children, Epidemiologic version (KSADS-E) and administration of the Conners' Adult ADHD Rating Scale (CAARS);
* Healthy males or females aged 21 to 45 years;
* A body mass index (BMI) between 18 and 30;
* Ability and willingness to provide written consent, comply with study instructions, and commit to all study visits and procedures;
* Adequate means of contacting the investigator in case of emergency or have means to be contacted readily by the investigator;
* No medical contraindications determined by the following: an adequate medical history, a physical examination including vital signs, 12-lead electrocardiogram (ECG); complete blood count with differential liver function and blood chemistry tests and urinalysis, including urine sample for drug screening;
* A negative urine drug test (barbiturates, benzodiazepines, amphetamines, opiates, cocaine, cannabinoids, ethanol) at screening, and at each laboratory day;
* Subjects must be non-smokers. A breath sample analysis will be conducted on-site with an Alco-Sensor Intoximeter, and an Innovative Medical Monitoring carbon monoxide (CO) Monitor, and must reveal a CO value of less than or equal to 8 ppm and a negative cotinine urine or saliva test (\>100 ng/mL);
* Females must have a negative pregnancy test (beta human chorionic gonadotrophin) at screening, and prior to each study drug administration. Females capable of childbearing are required to use a medically accepted form of contraception for at least 1 month prior to study start, throughout the study duration, and for at least 1 month after study medication is discontinued.
Exclusion Criteria:
* Current participation in the follow-up period of a preceding drug research study;
* Presence of unresolved/unstable psychiatric comorbidities as determined by clinical assessment and structured clinical interview using the SCID-1, that could interfere with study evaluations or affect a subject's safety;
* Recent history of drug addiction and/or alcoholism; and nicotine dependence within the past 6 months, as determined by psychiatric clinical assessment;
* Current significant acute or chronic medical disease, or any historical medical condition that could relapse during or immediately after the study and, in the investigator's opinion, may interfere with study evaluations or affect a subject's safety;
* Presence of potential organic etiology (e.g., a serious head injury or injury resulting in loss of consciousness, seizure disorder, thyroid problems, etc.) for ADHD symptomatology, as determined by clinical assessment;
* Blood pressure over 160/100 mmHg or under 90/40 mmHg, or heart rate over 120 beats per minute or below 40 beats per minute, obtained on two consecutive measures over 15 minutes when the subject is at rest;
* Exposure to any investigational new drug within 30 days of screening;
* Regular use of any prescription, over-the-counter drugs or likely need for concomitant treatment medication during the study period;
* Use of herbal products, including St. John's Wort, for 2 weeks prior to study initiation and throughout the study duration.