Hello At the night your friend do a variety of things with full consciousness but upon waking forget everything. This is a main problem even at the age of 16 years . He is taking prozac i.e. FLUOXETINE . The side effects of prozac are nervousness , insomnia , anxiety , headache , tremor drowsiness , seizures , MANIA , vomiting, sweating , dry mouth, hyponateremia etc . In your friend case at least one thing I can say that this temporary loss of memory ( amnesia ) is not a side effect of prozac ( so I mentioned in detail side effects of prozac) . In my so many patients I have noted that after taking of this drug so many complaints that they are feeling lightheadedness , fullness in epigastrium and increase in appetite but fullness in stomach . Due to anxiety of nervousness your friend may have behaving like this . In my opinion decrease the dose of prozac 1/2 than at present he is taking . If no relief then consult your treating doctor and get his opinion. Hope this will help you.