Verified answer

No, there are patients who take up to 300mg daily will little to no side effects so 400mg will not kill you, even though it could hurt you:http://www.drugs.com/dosage/amitriptyline.html.

However, in the event of an actual overdose, amitryptiline can be very deadly. It has avery narrow therapeutic window, meaning the dose needed for treatment is very close to the dose where worry-some side effects start. 750mg can result in extreme toxicity: http://tinyurl.com/9nhn7z4

Hope this answered your question.

Yes ,yes it would, really fast, she would croak