I am in the dark here gness as I am not sure what drug you are talking about. Looking at the doses that you have given me I am assuming that you aretalking about 40 mgms of Frusemide and 240 mgmsof a drug called Azosemide which is long acting.
Frusemide 40 mgms is a modest dose Azosemide 240mgms is a high dose.
Both drugs are diuretics and both lower the BP.
You are correct, the symtoms that your friend has could be due to low BP or dehydration through excess peeing.
However if my suppositions re drug identification then forget my post.