Although Macrobid (nitrofurantoin monohydrate; nitrofurantoin macrocrystals) capsules contain a dry powder and is not technically an extended release product (more on this below), they are not recommended to be opened. They should be swallowed whole. This is for a few reasons:
- Nitrofurantoin has been reported to cause esophageal irritation when applied directly to mucus membranes in the mouth and throat. The capsule protects the powder from coming into contact with these areas, and improves tolerability.
- Macrobid capsules actually contain two forms of nitrofurantoin, "monohydrate" and "macrocrystals". The macrocrystalline form is more slowly absorbed due to a slower rate of dissolution. This form can produce fewer adverse gastrointestinal effects. However, if it comes into contact with saliva/gastic juices early, it may dissolve faster, causing more side effects.
- Macrobid, in a technical sense, is not an extended release product as the capsule itself does not have extended release properties. However, when exposed to gastric and intestinal fluids, the nitrofurantoin monohydrate component of Macrobid forms a gel matrix and releases nitrofurantoin over time. This is why it is able to be dosed only twice a day, when compared to other nitrofurantoin products (e.g. Macrodantin), which need to be dosed four times a day. Opening Macrobid capsules and taking the powder can cause the gel matrix to form to early, creating a choking hazard and potentially altering the extended release properties.
If you are unable to take the capsule form, it is available in a liquid suspension dosage form in a strength of 25mg/mL. Ask your doctor if they are able to prescribe that for you instead. It is specifically formulated not cause the mouth/throat irritation the powder form can cause.