Do NOT use Nitrofurantoin if:

• you are allergic to any ingredient in Nitrofurantoin
• you are pregnant and at term (38 to 42 weeks pregnant), you are about to go into labor, or you are in labor
• you have decreased kidney function, decreased urination, or you are unable to urinate
• you have a history of liver problems or yellowing of the skin or eyes after taking any form of Nitrofurantoin
• the patient is younger than 1 month old.

Contact your doctor or health care provider right away if any of these apply to you.

Some medical conditions may interact with Nitrofurantoin. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have anemia, diabetes, electrolyte problems, glucose-6-phosphate dehydrogenase (G6PD) deficiency, kidney problems, liver problems, nerve problems (eg, peripheral neuropathy), porphyria (a certain blood problem), or low levels of vitamin B in your blood
• if you have a history of lung problems (eg, diffuse interstitial pneumonitis, pulmonary fibrosis)
• if you have very poor health.

Some medicines may interact with Nitrofurantoin. Tell your health care provider if you are taking any other medicines, especially any of the following:

• Probenecid or sulfinpyrazone because they may increase the risk of Nitrofurantoin's side effects or decrease Nitrofurantoin's effectiveness.

This may not be a complete list of all interactions that may occur. Ask your health care provider if Nitrofurantoin may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

Important safety information:

• Nitrofurantoin may cause drowsiness or dizziness. These effects may be worse if you take it with alcohol or certain medicines. Use Nitrofurantoin with caution. Do not drive or perform other possible unsafe tasks until you know how you react to it.
• Nitrofurantoin may rarely cause severe and sometimes fatal lung problems. If this occurs, it is usually in patients who take Nitrofurantoin for 6 months or longer. These problems may occur without warning signs. If you will be using Nitrofurantoin for a long period of time, your doctor may perform lung function tests to check for side effects. Tell your doctor right away if you develop fever, chills, chest pain, unusual cough, trouble breathing (especially while you are being active), other breathing problems, or persistent feeling of being unwell.
• Nitrofurantoin may rarely cause severe and sometimes fatal liver problems. Tell your doctor right away if you develop yellowing of the skin or eyes; pale stools; or severe or persistent nausea, loss of appetite, or stomach pain.
• Nitrofurantoin may rarely cause severe and sometimes fatal nerve problems. The risk may be greater in patients who have decreased kidney function, anemia, diabetes, electrolyte problems, or low blood vitamin B levels. Tell your doctor right away if you develop numbness, burning, or tingling in the hands or feet.
• Mild diarrhea is common with antibiotic use. However, a more serious form of diarrhea (pseudomembranous colitis) may rarely occur. This may develop while you use the antibiotic or within several months after you stop using it. Contact your doctor right away if stomach pain or cramps, severe diarrhea, or bloody stools occur. Do not treat diarrhea without first checking with your doctor.
• Long-term or repeated use of Nitrofurantoin may cause a second infection. Tell your doctor if signs of a second infection occur. Your medicine may need to be changed to treat this.
• Nitrofurantoin only works against bacteria; it does not treat viral infections (eg, the common cold).
• Be sure to use Nitrofurantoin for the full course of treatment. If you do not, the medicine may not clear up your infection completely. The bacteria could also become less sensitive to this or other medicines. This could make the infection harder to treat in the future.
• Nitrofurantoin may discolor the urine. This is normal and not a cause for concern.
• Diabetes patients - Nitrofurantoin may cause the results of some tests for urine glucose to be wrong. Ask your doctor before you change your diet or the dose of your diabetes medicine.
• Lab tests, including liver function, kidney function, and lung function, may be performed while you use Nitrofurantoin. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
• Use Nitrofurantoin with caution in the elderly; they may be more sensitive to its effects, especially lung or liver problems.
• Nitrofurantoin should not be used in children younger 1 month; the risk of anemia may be greater in these children.
• Pregnancy and breast-feeding: If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using Nitrofurantoin while you are pregnant. Do NOT take Nitrofurantoin if you are at term (38 to 42 weeks pregnant), if you are about to go into labor, or if you are in labor. Nitrofurantoin is found in breast milk. Do not breast-feed infants younger 1 month while you are taking Nitrofurantoin. If your child is older than 1 month, check with your doctor. Discuss any possible risks to your baby.

All medicines may cause side effects, but many people have no, or minor, side effects.

Check with your doctor if any of these most common side effects persist or become bothersome:

Gas; headache; loss of appetite; mild diarrhea; nausea.

Seek medical attention right away if any of these severe side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue; unusual hoarseness); bloody or watery stools; bluish skin or nails; blurred vision or other vision changes; butterfly-shaped rash on the nose and cheeks; confusion; joint or muscle pain; mood or mental changes (eg, depression); persistent feeling of being unwell; persistent headache; red, swollen, blistered, or peeling skin; severe or persistent diarrhea; severe stomach pain or cramps; symptoms of liver problems (eg, yellowing of the eyes or skin, pale stools, severe or persistent nausea or loss of appetite, stomach pain); symptoms of lung problems (eg, fever, chills, chest pain, shortness of breath, unusual or persistent cough); tingling, numbness, or burning of the hands or feet; unusual bruising or bleeding; unusual tiredness or weakness.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.