Is it obligatory to inform one's brother about medicine taken without his knowledge, or is it sufficient to return its value without informing him, especially given the fear of his reaction?

It is permissible to eat from a brother's house if his consent is known, based on the words of Allah Almighty: "There is no blame upon the blind, nor any blame upon the lame, nor any blame upon the sick, nor upon yourselves to eat from your houses, or the houses of your fathers, or the houses of your mothers, or the houses of your brothers, or the houses of your sisters, or the houses of your paternal uncles, or the houses of your paternal aunts, or the houses of your maternal uncles, or the houses of your maternal aunts, or [from houses] whereof you possess the keys, or [from the house] of your friend. There is no blame upon you whether you eat together or separately." (An-Nur: 61).

However, if his consent is not known, what was taken, or its equivalent value, must be returned to him, without informing him if that would cause harm.