Clinical Research Directory

Inclusion Criteria: * Children aged 6 months to 18 years with SNI (from any cause) with unexplained pain and irritability and whose cognitive or communication impairments prevent determination of pain location, cause, and type will be eligible to participate. * Eligible children will have cognitive impairment or be non-verbal and have severe levels of disability equivalent to Gross Motor Functional Classification System (GMFCS) scores of 3, 4 or 5 as well as Communication Function Classification System (CFCS) level 4 or 5. * Eligible children will score \>3 on two scales administered via an Eligibility Screening that measures persistence and distress level the child is experiencing as well as identifies the type of pain and irritability as PIUO - with no obvious cause or explanation. The score of \>3 on the scale measuring pain persistence and distress level confirms that the child is experiencing pain and irritability more than "a little" on "some days". * The will be evidence of a comprehensive evaluation of PIUO in the child's medical history, showing no evidence for treatable sources (nociceptive-inflammatory) of pain and/or irritability symptoms. Exclusion Criteria: * Children not within the specified age range * Children with communication capabilities and cognitive development to localize their pain. * Participants whose pain and or irritability is diagnosed through completion of the PIUO Pathway during the enrollment phase of the trial. * Patients with a known hypersensitivity/allergy to the study medication * Patients who are actively participating in another experimental therapy study for pain and/or irritability. * Patients who are a poor medical risk because of other systemic diseases or active uncontrolled infections. * Patients who score A or B on the Pain Survey * Patients who have an active source of nociceptive-inflammatory pain at the time of enrolment (e.g., post-operative pain) * Patients with active renal disease, known renal impairment or glomerular filtration rate \< 60 mL/min/1.73 m2 (if known). * Patients with known significant hepatic impairment at the discretion of the investigator. * Patients with clinically relevant abnormal ECG (if available) at the discretion of the investigator. * Patients with diagnosis of sickle cell disease. * Parents who do not speak one of Canada's two official languages (English or French)