Does amantadine maintain function in long-established brain injury? A single case experimental design

Nicky Haire - ORCID: 0000-0003-1178-2960 https://orcid.org/0000-0003-1178-2960Research into the role of dopamine agonist (DA) use in acquired brain injury (ABI) has primarily identified roles in restoration of consciousness and cognition in the acute or recovery phase following injury (1-5). The role of DA in later functional recovery is less well defined. We report a single case experimental design (SCED) demonstrating amantadine associated functional improvement, six years following severe TBI. Upon recruitment, the patient had been prescribed amantadine for the previous two years based on reported subjective improvement. This trial was devised as a means of justifying continued use. A scoring system was developed based on established abilities in managing of personal care and social interaction. Specific tasks were identified within which up to 7 component actions were identified, with 34 actions described in total. Each component action was graded on a ranked scale of 1 to 4 to based on quality of response to a given request, or the extent of prompting required to elicit response. Using a SCED format, actions were scored at baseline while continuing with amantadine use, and at intervals following withdrawal, and reintroduction. Daytime sleep duration was also recorded. At 3rd and 5th weeks post withdrawal, deterioration was recorded in 27 of the 34 graded activities. At 3rd and 5th weeks following reintroduction, all but 3 actions were graded at baseline or higher. Duration of afternoon sleep increased from 35 minutes to 80 minutes during the trial withdrawal period returning toward baseline on resumption of amantadine. This outcome supports a view that amantadine may have a role in sustaining long-term functional benefit following severe TBI. The model used suggests potential to use similar client specific measures of outcome in an SCED model as a template to capture change in a larger scale trial.https://doi.org/10.1080/02699052.2021.197234135pubpub1