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Macrobid Prescribing Information

Macrobid is the brand name for a medication called nitrofurantoin. Nitrofurantoin is an antibiotic commonly used to treat urinary tract infections (UTIs) caused by certain types of bacteria. It works by interfering with the growth and reproduction of bacteria, helping to eliminate the infection.

Antibiotic is often prescribed for uncomplicated UTIs, such as cystitis, which primarily affect the lower urinary tract. It may not be as effective for more severe or complicated infections that involve the kidneys or other parts of the urinary system.

Macrobid capsules

Uses of Macrobid

Macrobid is primarily used for the treatment and prevention of urinary tract infections (UTIs), particularly those caused by susceptible strains of bacteria. Here are some specific uses:

  • Uncomplicated Urinary Tract Infections (Cystitis): Medicine is commonly prescribed to treat uncomplicated UTIs that affect the lower urinary tract, such as cystitis. It can help alleviate symptoms like pain, burning, and frequent urination.
  • Prophylaxis (Prevention) of UTIs: In some cases, Macrobid may be prescribed for prophylactic use, meaning it's taken regularly to prevent recurrent UTIs in individuals who are prone to getting them.
  • Bacterial Susceptibility: Macrobid is effective against certain bacteria commonly associated with UTIs, such as Escherichia coli (E. coli), which is a common cause of these infections.

It's important to note that Macrobid is not effective against all types of bacteria, and its use should be guided by the results of bacterial culture and sensitivity tests. Additionally, medicament is not suitable for treating more severe or complicated urinary tract infections that involve the kidneys (pyelonephritis) or other parts of the urinary system.


The dosage of Macrobid can vary depending on the specific infection being treated, the patient's age, weight, kidney function, and other factors. The following dosages are general guidelines and may not apply to everyone:

Adults for Uncomplicated UTIs (Cystitis):

  • The typical dose is usually 100 mg of Macrobid twice a day (every 12 hours) for 3 days.
  • It's recommended to take the doses with food to enhance absorption and reduce the risk of stomach upset.

Prophylactic Use to Prevent UTIs:

  • The usual dose for prophylaxis is 50 to 100 mg of Macrobid once daily, often taken at bedtime.

Dosage for Patients with Impaired Kidney Function:

  • For patients with reduced kidney function, the dosage of Macrobid may need to be adjusted to avoid potential side effects or toxicity.

It's important to take the full course of antibiotics as prescribed, even if you start feeling better before completing the treatment. If you miss a dose, take it as soon as you remember, unless it's close to the time for the next dose. In that case, skip the missed dose and continue with your regular dosing schedule.

Side Effects of Macrobid

Macrobid can cause a range of side effects, although not everyone will experience them. Common side effects are usually mild and may include:

Gastrointestinal Effects:

  • Nausea
  • Vomiting
  • Loss of appetite
  • Abdominal pain or discomfort
  • Diarrhea
  • Headache: Some individuals may experience headaches while taking Macrobid
  • Dizziness: Macrobid can sometimes cause dizziness or a feeling of lightheadedness

Respiratory Symptoms:

  • Shortness of breath
  • Cough

Skin Reactions:

  • Rash
  • Itching
  • Hives (urticaria)
  • Changes in Urine Color: Nitrofurantoin can cause the urine to turn a dark yellow or brown color. This is harmless and temporary.
  • Peripheral Neuropathy: In rare cases, prolonged use of Macrobid can lead to nerve damage known as peripheral neuropathy, which may cause symptoms like numbness, tingling, or weakness in the hands or feet.
  • Hematologic Effects: Macrobid may rarely affect blood cell counts, leading to conditions like anemia or decreased platelet count.

It's important to note that severe allergic reactions to Macrobid are rare but can occur. Seek medical attention immediately if you experience symptoms such as difficulty breathing, severe rash, swelling (especially of the face, lips, or throat), or intense itching.

Interaction with other drugs

Macrobid can interact with other drugs, potentially affecting their effectiveness or increasing the risk of side effects. Here are some examples of drug interactions to be aware of:

  • Antacids Containing Magnesium Trisilicate: Taking antacids containing magnesium trisilicate along with Macrobid can reduce the absorption of nitrofurantoin, potentially making the medication less effective. If you need to take an antacid, it's advisable to do so at least two hours before or after taking antibiotic.
  • Probenecid: Probenecid, a medication used to treat gout, can interfere with the elimination of nitrofurantoin from the body, leading to higher levels of the antibiotic in the bloodstream. This could increase the risk of side effects.
  • Drugs that Affect Liver Enzymes: Some medications that affect liver enzymes, such as enzyme inducers or inhibitors, can alter the metabolism of nitrofurantoin. This could affect how quickly the drug is broken down and removed from the body.
  • Medications That Cause Lung Problems: Macrobid can rarely cause lung problems, and taking other medications that have similar effects could increase this risk. These include drugs known as pulmonary toxicants.
  • Other Antibiotics: Taking Macrobid along with other antibiotics might lead to a decreased effectiveness of one or both medications.
  • Medications That Affect Urinary pH: Drugs that affect the acidity or alkalinity of the urine can influence the effectiveness of nitrofurantoin.
  • Vitamin B12 Deficiency: Long-term use of nitrofurantoin has been associated with a risk of vitamin B12 deficiency. If you are taking medications or supplements that affect vitamin B12 levels, this could compound the risk.

What to avoid while on Macrobid

While taking Macrobid, there are certain things you should avoid to ensure the medication's effectiveness and reduce the risk of potential side effects. Here are some recommendations:

  • Alcohol: It's generally advised to avoid alcohol while taking Macrobid. Alcohol consumption can interfere with the body's ability to metabolize the medication and may increase the risk of side effects.
  • Antacids: If you need to take antacids for digestive issues, avoid using antacids that contain magnesium trisilicate while you are on Macrobid. These antacids can reduce the absorption of the antibiotic, potentially making it less effective. If you must take an antacid, do so at least two hours before or after taking this drug.
  • Other Antibiotics: Taking multiple antibiotics simultaneously could lead to decreased effectiveness or increased side effects.
  • Medications That Affect Urinary pH: Certain medications can alter the pH (acidity or alkalinity) of your urine, potentially affecting the effectiveness of Macrobid.
  • Medications That Impact Liver Enzymes: These medications can impact the metabolism of Macrobid and other drugs, potentially leading to interactions.
  • Vitamin B12 Supplements: Long-term use of Macrobid has been associated with a risk of vitamin B12 deficiency.
  • Driving and Operating Machinery: Medicament can cause dizziness in some individuals. If you experience dizziness or any other side effects that could impair your ability to drive or operate machinery, avoid these activities until you are sure of how the medication affects you.
  • Sun Exposure: While there isn't a specific interaction between Macrobid and sunlight, some antibiotics can make your skin more sensitive to sunlight. It's always a good idea to use sunscreen and protective clothing if you'll be spending time outdoors.
  • Smoking: Although there is no specific interaction between Macrobid and smoking, it's generally a good idea to avoid smoking while on antibiotics. Smoking can affect your body's ability to heal and recover from infections.

Contraindications of Macrobid

Nitrofurantoin has certain contraindications, which are specific conditions or situations in which the use of the medication is not recommended due to the potential risks outweighing the benefits. Here are some contraindications to be aware of:

  • Known Allergy to Nitrofurantoin: If you have a known hypersensitivity or allergy to nitrofurantoin or any of its components, you should not take capsules.
  • Severe Kidney Impairment: Macrobid is primarily eliminated from the body through the kidneys. If you have severe kidney impairment or decreased kidney function, Macrobid may not be suitable for you due to the risk of toxicity and reduced effectiveness.
  • G6PD Deficiency: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a genetic condition that affects the red blood cells. Nitrofurantoin can trigger hemolysis (destruction of red blood cells) in individuals with G6PD deficiency, so its use is generally contraindicated in such cases.
  • Pregnancy at Term (38-42 Weeks): Drug should not be used in pregnant women at term (38-42 weeks of gestation) or during labor and delivery, as it may cause hemolytic anemia in the newborn.
  • Infants Under One Month of Age: Macrobid is not recommended for infants under one month of age due to the risk of hemolytic anemia.
  • Severe Liver Impairment: If you have severe liver impairment or liver disease, your ability to metabolize and eliminate Macrobid may be compromised, increasing the risk of side effects.
  • Porphyria: Porphyria is a group of rare genetic disorders that affect the nervous system or skin. Macrobid can exacerbate certain types of porphyria, so its use is generally contraindicated in individuals with this condition.
  • Laboratory Testing: The contraindication for using Macrobid for diagnosing urinary tract infections is that it may interfere with laboratory tests for urine glucose (sugar) using copper reduction methods (Benedict's solution, Fehling's solution, or Clinitest).

Pregnancy and Macrobid

Macrobid use during pregnancy requires careful consideration and medical supervision. The safety of antibiotic during pregnancy depends on several factors, including the stage of pregnancy, the potential benefits, and the risks to both the mother and the developing fetus. Here's what you need to know:

  • Risk Categories: In the United States, medications are categorized into different risk categories based on their potential effects during pregnancy. Macrobid is generally classified as a Category B medication, which means that animal studies have not shown a risk to the fetus, but there is limited data available for human use.
  • First Trimester: When considering Nitrofurantoin use during the first trimester (weeks 1-13), some studies suggest that there might be a slightly increased risk of birth defects. However, the overall risk is still considered low.
  • Neonatal Hemolysis: There is a concern that Macrobid taken by the mother near the time of delivery (at term) or during labor could cause hemolytic anemia in the newborn. For this reason, Macrobid is generally avoided in pregnant women at term (38-42 weeks of gestation) and during labor and delivery.
  • Alternative Treatments: In some cases, your doctor might consider alternative antibiotics that are known to be safer during pregnancy, especially if you're in the first trimester. Cephalosporins and penicillins are among the antibiotics that are often considered safer options for treating UTIs during pregnancy.
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