The role of amantadine in cognitive recovery early after traumatic brain injury: A systematic review

We conducted an updated systematic review on the safety and efficacy of amantadine in cognitive recovery after traumatic brain injury (TBI), in order to determine if the current literature justifies its use in this clinical condition. A comprehensive search strategy was applied to three databases (PubMed, Scopus, and Cochrane). Only randomized clinical trials (RCTs) that compared the effect of amantadine and placebo in adults within 3 months of TBI were included in the review. Study characteristics, outcomes, and methodological quality were synthesized. This systematic review was conducted and presented in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). A quantitative synthesis (meta-analysis) was not feasible due to the large heterogeneity of studies identified. Three parallel RCTs and one cross-over RCT, with a total of 325 patients were included. All of the studies evaluated only severe TBI in adults. Amantadine was found to be well tolerated across the studies. Two RCTs reported improvement in the intermediate-term cognitive recovery (four to six weeks after end of treatment), using DRS (in both studies) and MMSE, GOS, and FIM-Cog (in one study). The effect of amantadine on the short-term (seven days to discharge) and long-term (six months from the injury) cognitive outcome was found not superior to placebo in two RCTs. The rate of severe adverse events was found to be consistently very low across the studies (the incidence of seizures, elevation in liver enzymes and cardiac death was 0.7 %, 1.9 %, and 0.3 %, respectively). In conclusion, amantadine seems to be well tolerated and might hasten the rate of cognitive recovery in the intermediate-term outcome. However, the long-term effect of amantadine in cognitive recovery is not well defined and further large randomized clinical trials in refined subgroups of patients are needed to better define its application.