Why can't you mix grapefruit juice with valium?

Can't mix it with statins either, but I only found out about valium(diazepam) recently. What about antididepressants?
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Grapefruit juice is a potentiate of benzos. One of the enzymes prevents Valium from breaking down properly when it's normally absorbed, and the levels in your blood can become dangerously high and cause more side effects or impair you.

It actually takes a large amount of grapefruit juice to cause this, and Valium is pretty weak to begin with, but the pharmacy is required to put the warning label on it anyway.