I understand that your grandfather is experiencing health symptoms and you are concerned for his well being. You appear to be a very caring grandchild and he's lucky to have you involved in his care. According to Aricept safety information, side effects of Aricept can include nausea, vomiting, diarrhea, bruising, insomnia, muscle cramps, loss of appetite, and fatigue. The new onset of severe headaches and really high blood pressure may be due to an interaction with other medications, or it may have nothing to do with the Aricept at all. The best way to find out is to seek medical consultation as soon as possible. Your grandfather may have to undergo testing in order to find out the cause behind the problem. I wish him the very best!