Dose Finding Study in Adults With Attention-Deficit/Hyperactivity Disorder (ADHD)(174007/P05805/MK-8777-003)

Inclusion Criteria

• are between 18-50 years, inclusive;
• are male; or female who are non-pregnant, non-lactating and using an acceptable method of birth control (intrauterine device, double-barrier method, hormonal contraceptives); or female of non-childbearing potential if they are a) surgically sterile (tubal ligation, hysterectomy and/or bilateral oophorectomy) and provide documentation of the procedure by operative report or ultrasound scan, or b) post-menopausal for greater than one year with follicle stimulating hormone (FSH) level greater than or equal to 40 mIU/mL at screening. All females must have a negative serum pregnancy test at screening;
• are outpatients;
• provide written informed consent
• are fluent in the language of the investigator,
• are able to discontinue the use of any psychotropic medications for the treatment of ADHD symptoms at screening;
• meet strict operational criteria for adult ADHD according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV-TRTM)
• have a Clinical Global Impression ADHD score of 4 or higher at screening

Exclusion Criteria

• have any clinically significant concurrent medical condition (endocrine, renal, respiratory, cardiovascular, hematological, immunological, cerebrovascular, neurological, anorexia, obesity or malignancy) that has become unstable and may interfere with the interpretation of safety and efficacy evaluations.
• have any clinically significant abnormal laboratory, vital sign, physical examination, or electrocardiogram (ECG) findings at screening that, in the opinion of the investigator, may interfere with the interpretation of safety or efficacy evaluations.
• have any history of liver disease (e.g., cirrhosis, hepatitis), or liver injury;(history of hepatitis A greater than one year prior to screening is acceptable); any abnormal clinically significant findings at screening on liver laboratory parameters (serum glutamic-pyruvic transaminase [SGPT], serum glutamic oxaloacetic transaminase [SGOT], gamma-glutamyltransferase [GGT], lactate dehydrogenase [LDH], bilirubin, albumin, protein, alkaline phosphatase);
• have a seizure disorder beyond childhood or are taking any anticonvulsants to prevent seizures;
• have known serological evidence of human immunodeficiency virus (HIV) antibody;
• have a positive test result at screening on hepatitis B surface antigen or hepatitis A immunoglobulin M (IgM) antibodies or hepatitis C total antibodies;
• are pregnant as confirmed by a positive serum pregnancy test at screening;
• have QTc values >450 msec at screening using Fridericia's QTc formula;
• have a confirmed positive result in the alcohol/drug screen test for alcohol, illegal or non-prescribed drugs at screening (except marijuana/ tetrahydrocannabinol [THC]);
• have a confirmed positive result in the alcohol/drug screen re-test for marijuana/THC;
• have current or lifetime history of bipolar and psychotic disorders;
• have a current major depression disorder, obsessive-compulsive disorder, post-traumatic stress disorder, generalized anxiety disorder, panic disorder and eating disorder (also if treated but not currently symptomatic);
• have a current comorbid dysthymia or social anxiety disorder that is currently treated with psychotropic medication;
• have a current untreated social anxiety disorder that may interfere with the assessment of ADHD in the investigator's opinion;
• present an imminent risk of self-harm or harm to others;
• have any history of a significant suicide attempt, or possess a current risk of attempting suicide, in the investigator's opinion, based on clinical interview and responses provided on the Beck Scale for Suicidal Ideation (BSS);
• have a history of jailing or imprisonment in the past 6 months due to worsening of symptoms of ADHD;