Study to Assess the Safety of Amantadine Hydrochloride (HCl) Intravenous (IV) Solution (MR-301) in Patients With Severe Traumatic Brain Injury (TBI).

Inclusion Criteria: 1. Age: 18 to 75 years. 2. Patients with TBI confirmed by CT scan or MRI 3. Patient have sustained a trauma between 72 hours to 1 week 4. Patient with Abbreviated Injury Score (AIS) ≤ 2. 5. Patients must be admitted to an acute care setting no less than 2 days prior to randomization. 6. Glasgow Coma Score of 3 to 8, inclusive. 7. Patients must be unable to consistently follow commands or to engage in functional communication, as assessed by the score on the CRS-R. 8. Patients have at least one reactive pupil. 9. Must have a Legally Authorized Representative (LAR) able to provide consent for the trial. 10. Patient must have stable vitals ---Intracranial pressure ICP Value is at discretion of investigator), systolic blood pressure (SBP\>90 mmHg) partial pressure of oxygen (PaO2 \> 60 mmHg)\]. Exclusion Criteria: 1. Life expectancy of less than 24 hours. 2. Patient has any spinal cord injury. 3. Patient has a penetrating head injury. 4. Patient has bilaterally fixed dilated pupils 5. Patients with history of any medical or psychiatric disorder, or any severe concomitant disease that would, in the opinion of the Investigator, interfere with clinical assessment. 6. Patient has poorly controlled seizure more than one per month. 7. Prior history of status epilepticus 8. Prior treatment with or a sensitivity to amantadine HCl or amantadine. 9. Patient has screening lab measurements outside the normal range 1. Absolute neutrophil count (ANC): ≤ 1.5 x 109/L 2. Hemoglobin ≤ 8 g/dL or active bleeding requiring ongoing transfusions. 3. Platelets ≤ 80 x 109/L or active bleeding requiring ongoing transfusions. 4. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) or total bilirubin (unless isolated Gilbert's syndrome) ≥ 2x the upper limit of normal (ULN) 5. Estimated glomerular filtration rate (eGFR) \< 60 ml/min/1.73m2 10. Patient has received treatment with an investigational drug, CNS stimulant or dopamine antagonist/agonist within 4 weeks. 11. Patient has a history of NYHA Class 3 or Class 4 Congestive Heart Failure within the last 5 years. 12. Females who are nursing, pregnant, or planning to become pregnant 13. any other clinically significant medical condition as determined by the Investigator, that may unfavorably alter the risk benefit of study participation. 14. Patient has prolonged QT interval. 15. Treatment with a systemic anticholinergic medication within 1 week prior to screening.