Isshuukan ni vs isshuukan de?

Question:

I've heard both used in similar context and I can't determine the difference between the two.
Ex:
先週一週間で２０本以上のビールを飲みました。
Can you also use に instead of で in this situation to keep the meaning the same?

also, I saw 一週間に薬を二回飲みます。
Can you use で in stead of に in this situation?

Is there a slight difference in undertone or meaning if one is used instead of the other?


よろしくお願いします。

Answer:

There is practically little difference in this case. It's not the case in other contexts, though.