One part of the novel has always mystified me, given that I have only a rudimentary knowledge of medicines and the human heart…
The demon vows to kill Regan by depriving her body of sleep, eventually inducing a heart attack. If so, why does Karras administering such an excessive dosage of the tranquillizer work in its favour? Is it because the body fighting such a high amount of Librium will hasten cardiac arrest even faster due to physical stress?