Inclusion Criteria:  Subject has a body mass index (BMI) of 18 to 32 kg/m2, inclusive. Healthy as determined by a responsible physician, based on medical evaluation including medical history, physical examination, concomitant medication, vital signs, 12-lead ECG, C-SSRS responses, and clinical laboratory evaluations.  Willingness to comply with requirements or the trial, including contraception requirements.  Able to give fully informed consent.  Exclusion Criteria:  Positive tests for hepatitis B & C, HIV. Clinically relevant history of abnormal physical or mental health. Clinically relevant abnormal laboratory results (including hepatic and renal panels, complete blood count, chemistry or coagulation panel and urinalysis), 12-lead ECG and vital signs, or physical findings.  History of severe adverse reactions or allergies, or history of an anaphylactic reaction to prescription or non-prescription medication or food.  Drug or alcohol abuse. Smoking. Use of medication that inhibits CYP2D6. Participation in other clinical trials of unlicensed medicines in the previous 3 months. Loss of more than 400 mL blood in the previous 3 months. Vital signs, QTcF interval or laboratory values outside the acceptable range. Predicted poor and intermediate CYP2D6 metabolisers. Clinically relevant abnormal findings at the screening assessment. History of epilepsy or seizures. Clinically relevant abnormal medical history or concurrent medical condition disease associated with cognitive impairment and/or psychosis. History of suicidal thoughts or ideation, or any history of insomnia. Use of tobacco and/or nicotine containing products within 90 days of dosing. Habitual and heavy consumption of caffeinated beverages. Consumption of cranberry, pomegranate, star fruit, grapefruit, pomelos, exotic citrus fruits or Seville oranges (including marmalade and juices made from these fruits) within 3 days before admission. Objection by General Practitioner