From the Guidelines
Macrobid (nitrofurantoin) commonly causes gastrointestinal side effects, including nausea, vomiting, loss of appetite, and diarrhea, affecting approximately 23-34% of patients taking the medication, as reported in studies such as Iravani et al (1999) and Christiaens et al (2002) 1.
Common Side Effects
- Gastrointestinal issues: nausea, vomiting, loss of appetite, and diarrhea
- Headache, dizziness, and dark yellow or brown urine discoloration, which is harmless but can be alarming if unexpected
- Mild skin rashes or itching
Reducing Side Effects
Taking Macrobid with food or milk can help reduce stomach upset.
Serious Side Effects
Less common but more serious side effects that require immediate medical attention include:
- Severe chest pain
- Difficulty breathing
- Signs of liver problems (yellowing of eyes/skin)
- Signs of nerve damage (numbness, tingling)
- Severe allergic reactions According to a study published in 2019, nitrofurantoin has potentially serious risks of pulmonary and hepatic toxicity, although the rates are extremely low, reported to be 0.001% and 0.0003%, respectively 1.
General Guidance
Macrobid works by directly attacking bacterial DNA, which explains why it can sometimes cause digestive upset as it affects bacteria in the gut. The medication is generally well-tolerated when taken as prescribed for the full course, typically 5-7 days for urinary tract infections, as recommended by guidelines such as those from the American College of Physicians in 2021 1.
From the FDA Drug Label
If the symptoms are not recognized as being drug-related and nitrofurantoin therapy is not stopped, the symptoms may become more severe. Acute pulmonary reactions are commonly manifested by fever, chills, cough, chest pain, dyspnea, pulmonary infiltration with consolidation or pleural effusion on x-ray, and eosinophilia Acute reactions usually occur within the first week of treatment and are reversible with cessation of therapy. Gastrointestinal: Nausea, emesis, and anorexia occur most often. Abdominal pain and diarrhea are less common gastrointestinal reactions. Neurologic: Peripheral neuropathy, which may become severe or irreversible, has occurred Fatalities have been reported. Asthenia, vertigo, nystagmus, dizziness, headache, and drowsiness also have been reported with the use of nitrofurantoin. Hypersensitivity reactions represent the most frequent spontaneously-reported adverse events in worldwide postmarketing experience with nitrofurantoin formulations
The most common side effects of Macrobid (nitrofurantoin) are:
- Gastrointestinal reactions:
- Nausea
- Emesis
- Anorexia
- Abdominal pain
- Diarrhea
- Hypersensitivity reactions
- Neurologic reactions:
- Asthenia
- Vertigo
- Nystagmus
- Dizziness
- Headache
- Drowsiness 2
From the Research
Common Side Effects of Macrobid
The most common side effects of Macrobid, also known as nitrofurantoin, include:
- Pulmonary adverse effects, such as acute hypersensitivity reactions and chronic reactions involving fibrosis 3, 4, 5, 6
- Hepatic adverse effects, such as hepatotoxicity 3
- Minor side effects or allergies, which were reported in 7% of patients in one study 3
- Respiratory failure, which can occur in severe cases of nitrofurantoin-induced chronic pulmonary toxicity 4, 6
Risk Factors for Side Effects
Certain factors can increase the risk of side effects from Macrobid, including:
- Chronic use of the drug, which appeared to be associated with a greater risk of serious side effects in one study 3
- Age, with older adults potentially being at higher risk of pulmonary and hepatic adverse effects 3, 4, 5, 6
Management of Side Effects
Management of side effects from Macrobid typically involves discontinuation of the drug, as well as symptomatic and supportive treatment 4, 5, 6. In some cases, corticosteroids may be used to relieve symptoms and hasten the resolution of pulmonary lesions, although the evidence for this is limited 4.