['attention deficit hyperactivity disorder (adhd)']
['prc-063 25 mg', 'placebo', 'prc-063 35 mg', 'prc-063 45 mg', 'prc-063 55 mg', 'prc-063 70 mg', 'prc-063 85 mg', 'prc-063 100 mg']

        Inclusion Criteria:

          -  Must be male or non-pregnant female at least 18 years of age and less than or equal to
             60 years of age.

          -  Must have an ADHD diagnosis, in attentive, hyperactive/impulsive or combined, as
             defined by the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition
             (DSM-5) based on clinician assessment using multiple informants and a structured
             interview.

          -  Clinician-completed ADHD-5-RS total score must be equal to or greater than 24, as
             assessed at Visit 2a.

          -  Must be unsatisfied with his or her current pharmacological therapy for treatment of
             ADHD or not currently receiving pharmacological therapy for ADHD. Inclusion of
             subjects naïve to pharmacological therapy for ADHD is permitted.

          -  Female subjects must be one of the following: a. surgically sterile prior to
             screening; b. if of childbearing potential, abstinent or willing to use a reliable
             method of contraception, such as oral contraceptive, two barrier methods, a barrier
             method plus a spermicidal agent.

          -  Female subjects of Child-Bearing Potential (FOCP) must be a negative serum β-hCG
             pregnancy test at screening.

          -  Must have a minimum level of intellectual functioning, as determined by an
             Intelligence Quotient (IQ) score of 80 or above based on the KBIT-2.

          -  Mentally and physically competent to sign an informed assent document, in the case of
             the subject, and an informed consent document, in the case of the parent/guardian,
             indicating that they understand the purpose of and procedures required for the study
             and are willing to participate in the study.

          -  Able and willing to comply with the study procedures for the entire length of the
             study, including a successful swallow test of an empty 100 mg capsule.

        Exclusion Criteria:

          -  Having an allergy to methylphenidate or amphetamines or a history of serious adverse
             reactions to methylphenidate.

          -  Known to be non-responsive to methylphenidate treatment. Non-response is defined as
             methylphenidate use at various doses for a phase of at least four weeks at each dose
             with little or no clinical benefit in the last 10 years.

          -  Being diagnosed with or having a history of strokes, epilepsy, migraine headaches
             (greater than 1 instance every two months), glaucoma, thyrotoxicosis, tachyarrhythmias
             or severe angina pectoris or have serious or unstable medical illness. Subjects with
             controlled or stable asthma or diabetes will be permitted.

          -  Elevated blood pressure, defined as any values above 89 diastolic or 139 systolic, as
             assessed at Visit 1.

          -  Clinically significant ECG abnormalities, as assessed at Visit 1.

          -  Clinically significant laboratory abnormalities, as assessed at Visit 1.

          -  Currently receiving guanethidine, pressor agents, MAO inhibitors, coumarin
             anticoagulants, anticonvulsants (e.g., phenobarbital, phenytoin, primidone),
             phenylbutazone, tricyclic antidepressants (e.g., imipramine, desipramine), selective
             serotonin reuptake inhibitors (SSRIs) or herbal remedies (unless on a stable dose for
             4 weeks).

          -  Subject has known history of symptomatic cardiovascular disease, advanced
             arteriosclerosis, structural cardiac abnormality, cardiomyopathy, serious heart rhythm
             abnormalities, coronary heart disease, transient ischemic attack or stroke or other
             serious cardiac problems that may place the subject at increased vulnerability to the
             sympathomimetic effects of a stimulant drug.

          -  Subject has a known family history of sudden cardiac death or ventricular arrhythmia.

          -  Subjects who are currently considered a suicide risk by the investigator.

          -  Having a primary diagnosis of schizophrenia, schizoaffective disorder, primary
             affective disorder, schizotypal personality, major depression, bipolar disorder,
             generalized anxiety, borderline personality disorder, antisocial personality or
             another unstable psychiatric condition requiring treatment, as assessed by the
             structured interview conducted at Visit 1.

          -  Having a history or suspected physiological dependence within the past 5 years
             (excluding nicotine) on narcotic analgesics or other psychoactive drugs (including
             barbiturates, opiates, cocaine, cannabinoids, amphetamines and benzodiazepines).

          -  Excessive consumption of alcohol (consumes alcohol in quantities greater than 15
             drinks per week; 1 drink is defined as 360 mL/12 oz. of beer, 120 mL/4 oz. of wine, or
             30 mL/1 oz. of hard liquor), or history (within previous 6 months) of alcohol abuse.

          -  Currently (or within 30 days before the planned start of treatment) receiving an
             investigational drug or using an experimental medical device.

          -  Homeless.
      