can produse gastritis
and bleeding sometime,but frank can not from anal canal
Blooding caused by advil when coming in the stool is not red but black, called malaena.
So threre may be some pathology in anal region,it may be haemorrhoid,fistula in ano etc.
So if bleeding is more you can take him to E.R.
Go for surgical opinion and stool test
ok and bye.