It sounds like you might need to do some additional evaluations to see if there’s a learning disability or other challenge also going on. It could be really poor working memory, which is common with ADHD. To my knowledge, there isn’t a medication that targets quicker thinking and reactions (definitely not ADHD medications).
Penny
ADDitude Community Moderator, Parenting ADHD Coach & Author, Mom to teen w/ ADHD, LDs, and autism