Currently, brand-name Macrobid is made by Norwich Pharmaceuticals, Inc., for Procter & Gamble Pharmaceuticals, Inc. Generic versions are made by various manufacturers.
Macrobid works in a unique way, compared to other antibiotics. In bacterial cells, the drug is changed into a highly reactive form that destroys certain bacterial proteins and molecules. As a result, the drug interferes with bacteria's ability to make essential cell components, such as protein, DNA, and cell walls.
Macrobid contains two forms of nitrofurantoin. Seventy-five percent of the nitrofurantoin is in the monohydrate form and is mixed with a special powder. In the digestive tract, the powder and the nitrofurantoin monohydrate form a gel that releases the medication slowly over time. Twenty-five percent of the drug is in the macrocrystalline form (the same form in Macrodantin®
, a similar antibiotic that must be taken four times a day, compared to just twice daily with Macrobid).