Ampicillin is a penicillin antibiotic. It is used to treat many gram-positive and gram-negative bacteria. The brand name of ampicillin is Principen; however, Principen is no longer available as a brand-name drug. The medication is available as the generic, ampicillin, as an oral capsule or as an injection
indicated for adults and children.
You should take ampicillin when your stomach is empty, which means taking your doses one hour before you eat any food, or waiting until two hours afterwards.
This is because your body absorbs less ampicillin after a meal, which means the medicine is less effective