Nitrofurantoin, sold under the trade name Macrobid among others, is an antibiotic used to treat bladder infections. It is not effective for kidney infections. It is taken by mouth. Common side effects include nausea, loss of appetite, diarrhea, and headaches.he most common side effects with nitrofurantoin are nausea, headache, and flatulence. Less common adverse events (occurring in less than 1% of those taking the drug) include: 1  Gastrointestinal: diarrhea, dyspepsia, abdominal pain, constipation, emesis. 2  Neurologic: dizziness, drowsiness, amblyopia.