Inclusion Criteria:
1. Participants had to be able to understand the nature of the study, agree to comply with the prescribed dosage regimens, report for regularly scheduled office visits, and communicate to study personnel about adverse events and concomitant medication use.
2. Participants must have met DSM-IV-TR diagnostic criteria for ADHD (Combined, Predominantly Inattentive or Predominantly Hyperactive-Impulsive Types) on the M.I.N.I.-Plus.
3. Participants must have had an ADHD-RS-IV score of greater than or equal to 28 at the placebo run-in baseline and CTN SR treatment baseline.
4. Participants must have had a Clinical Global Impression of Severity (ADHD version) score of greater than or equal to 4.
5. Participants must be able to read well enough to understand the informed consent form and other participant materials.
6. Participants must have been able to be reliably rated on the psychiatric scales required by the protocol based on investigator's judgment.
7. Participants must have been able to read and understand English.
8. Participants must have had a body mass index of approximately 18 to 35 kilograms/meter squared.
9. Sexually active, fertile males must have used effective birth control if their partners were women of childbearing potential. Women of childbearing potential (if a partner of a male participant) included any female who had experienced menarche and who had not undergone successful surgical sterilization or women on hormone replacement therapy with documented serum follicle stimulating hormone level greater than 35 milli-international units/milliliter. Even women who were using oral contraceptives, other hormonal contraceptives (vaginal products, skin patches, or implanted or injectable products), or mechanical products such as an intrauterine device or barrier methods (diaphragm, condoms, spermicides) to prevent pregnancy, or were practicing abstinence or where the partner was sterile (for example, vasectomy), should have been considered to be of childbearing potential.
Exclusion Criteria:
1. Participant had a DSM-IV-TR diagnosis of ADHD not otherwise specified.
2. Participants rated as having a greater than or equal to 30% improvement in ADHD symptoms or a score of less than 28 on the ADHD-RS-IV after Week 1 (placebo run-in). Such participants were withdrawn from the study prior to receiving any active drug.
3. Participant had a current or lifetime history of bipolar disorder or any psychotic disorder as established by M.I.N.I.-Plus.
4. Participant had a current history (past 90 days) of major depression, generalized anxiety disorder, obsessive-compulsive disorder, panic disorder or post-traumatic stress disorder as established by the M.I.N.I.-Plus.
5. History in the past 20 years of electroconvulsive therapy or lifetime history of vagal nerve stimulation or deep brain stimulation for the treatment of depression.
6. Participants with a history of drug or alcohol use disorders (abuse or dependence) must have been free of the diagnosis and of substance use for at least 6 months prior to the Screening visit.
7. Participant had a history of epilepsy, seizures, syncope, unexplained blackout spell(s), head trauma with clinically significant loss of consciousness or noninfantile febrile seizures.
8. Participant had a currently active medical condition (other than ADHD) that, in the opinion of the investigator, could have interfered with the ability of the participant to participate in the study safely.
9. Participant had a history of clinically significant, diagnosed cardiovascular disease of any kind, including uncontrolled hypertension. Participant had newly diagnosed cardiovascular disease of any kind in the investigator's judgment.
10. The participant had an intelligence quotient less than 80.
11. In the opinion of the investigator, the participant had not derived significant therapeutic benefit from 2 or more ADHD therapies given with an adequate dose and duration in adulthood (age 18 or older); that is, 1 failed course of treatment was acceptable, but 2 failed courses of treatment were not acceptable.
12. Participant taking medication specifically for treatment of ADHD symptoms (for example, stimulants, atomoxetine, tricyclic antidepressants, bupropion, modafinil) must have been off stimulants for 2 weeks and off nonstimulant ADHD therapies for 3 weeks prior to the placebo run-in visit and must have returned to the baseline level of ADHD symptoms in the opinion of the investigator. Participants must not have had evidence of a discontinuation or withdrawal reaction.
13. Participant was currently taking any antidepressant medication for any condition.
14. Participant was currently taking antipsychotic medication or an anticonvulsant medication (for example, phenytoin, carbamazepine, lamotrigine, or valproic acid) at anticonvulsant doses.
15. Participant had a known history of allergy to CTN.
16. Participant was unwilling to refrain from taking medications that may have interfered with the assessment of cognitive function and the assessment of sleep. Examples included benzodiazepines, sedating antihistamines, zolpidem, eszopiclone, and zaleplon. Herbal preparations with effects on the central nervous system also were prohibited throughout the study (for example, St. John's Wort or melatonin).
17. Participant had a history of sleep problems in the last 3 months.
18. Participant was unwilling to refrain from taking more than 1 unit of alcohol within 24 hours of the investigational center visits.
19. Participant was unwilling to restrict caffeine to no more than 500 mg/day (5 cups of coffee).
20. Participant was actively using any drugs with potential for abuse (for example, marijuana, cocaine, amphetamines).
21. Participant reported passive or active suicidal ideation or intent.
22. Participant was concurrently participating in another clinical research study or investigational drug study or had participated in such a study within the past 1 month.
23. Participant was at high risk of nonadherence to investigational product and the protocol regimen in the investigator's opinion.
24. Participant could not have begun psychotherapy during the study, but may have continued therapy at the same intensity and frequency, if begun at least 3 months prior to placebo run-in.
Exclusion Criteria, Physical and Laboratory Test Findings
1. Participants who had a positive urine drug screen, which could not be explained by prescribed medications. The urine drug screen may have been repeated based on investigator judgment.
2. Participants with clinically significantly abnormal thyroid-stimulating hormone or a positive result on a standard hepatitis-screening panel or human immunodeficiency virus screen. Note: Adequate thyroid replacement for a previously diagnosed thyroid deficiency, which had been stable for 3 months or more, was acceptable.
3. Participants with clinically significant laboratory abnormalities or with clinical laboratory values of potential clinical concern.
4. Diastolic blood pressure greater than 85 millimeters of mercury (mmHg) at placebo run-in.
5. Systolic blood pressure greater than 135 mmHg at placebo run-in.
6. Participant had a QT interval of greater than 450 milliseconds on 2 or more electrocardiogram tracings taken within 15 minutes, assessed with the participant in a supine position for 3 minutes.
Other Exclusion Criteria
1. Prisoners or participants who were involuntarily incarcerated.
2. Participants who had a compulsory detainment for treatment of either a psychiatric or a physical illness.
3. Participants who planned to have elective surgeries during the course of the study.
4. Participants with a history of antidepressant-induced hypomania or dysphoria.
