IPA: //æmˈnɛstɪk//
KK: /æmˈnɛstɪk/
Relating to or causing amnesia, which is a loss of memory.
The amnestic effects of the medication were concerning to the doctors.
Amnestic is derived from the Greek root "amnesia" (meaning forgetfulness) combined with the suffix "-tic" (meaning pertaining to). The word describes something that relates to or causes forgetfulness.
Think of 'amnesia' which means forgetfulness, and remember that 'amnestic' refers to something related to forgetting.