Macrobid 100mg Capsules
It is used to treat or prevent a urinary tract infection (UTI).
Drug Class
Urinary Anti-infective
Pharmacologic Class
Nitrofuran Derivative
Pregnancy Category
Category B
FDA Approved
Aug 1991
DEA Schedule
Not Controlled
Overview
What is this medicine?
Macrobid is an antibiotic used to treat and prevent urinary tract infections (UTIs). It works by stopping the growth of bacteria in the urine. It's important to take it exactly as prescribed, usually twice a day with food, and to finish the entire course of medication even if you feel better.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. Take your medication with food to help your body absorb it properly. Continue taking your medication as directed by your doctor or healthcare provider, even if you start to feel better.
It's also important to stay hydrated by drinking plenty of non-caffeinated liquids, unless your doctor advises you to limit your fluid intake. However, avoid taking antacids that contain magnesium trisilicate while taking this medication, as they may interact with it.
Storing and Disposing of Your Medication
To keep your medication effective and safe, store it at room temperature in a dry place, away from the bathroom. Keep all medications out of the reach of children and pets to prevent accidental ingestion. When you're finished with your medication or it expires, dispose of it properly. Do not flush it down the toilet or pour it down the drain unless instructed to do so by your doctor or pharmacist. If you're unsure about how to dispose of your medication, ask your pharmacist for guidance. You may also want to check if there are any drug take-back programs in your area.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for a missed one.
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. Take your medication with food to help your body absorb it properly. Continue taking your medication as directed by your doctor or healthcare provider, even if you start to feel better.
It's also important to stay hydrated by drinking plenty of non-caffeinated liquids, unless your doctor advises you to limit your fluid intake. However, avoid taking antacids that contain magnesium trisilicate while taking this medication, as they may interact with it.
Storing and Disposing of Your Medication
To keep your medication effective and safe, store it at room temperature in a dry place, away from the bathroom. Keep all medications out of the reach of children and pets to prevent accidental ingestion. When you're finished with your medication or it expires, dispose of it properly. Do not flush it down the toilet or pour it down the drain unless instructed to do so by your doctor or pharmacist. If you're unsure about how to dispose of your medication, ask your pharmacist for guidance. You may also want to check if there are any drug take-back programs in your area.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for a missed one.
Lifestyle & Tips
- Take with food or milk to improve absorption and reduce stomach upset.
- Drink plenty of fluids unless otherwise directed by your doctor.
- Complete the full course of medication, even if symptoms improve, to prevent recurrence and antibiotic resistance.
- Urine may turn dark yellow or brown; this is a harmless side effect.
Available Forms & Alternatives
Available Strengths:
Generic Alternatives:
Dosing & Administration
Adult Dosing
Standard Dose:
100 mg orally every 12 hours for 7 days
Dose Range:
100 - 100 mg
Condition-Specific Dosing:
uncomplicatedUTI:
100 mg orally every 12 hours for 7 days
Pediatric Dosing
Neonatal:
Contraindicated in infants less than 1 month of age
Infant:
Contraindicated in infants less than 1 month of age
Child:
Not recommended for children under 12 years of age due to dosage form (capsule) and potential for difficulty swallowing. For children 1 month to 12 years, nitrofurantoin suspension (macrocrystals) is typically used at 5-7 mg/kg/day in 4 divided doses.
Adolescent:
100 mg orally every 12 hours for 7 days (for those 12 years and older)
Dose Adjustments
Renal Impairment:
Mild:
No dosage adjustment needed if CrCl > 60 mL/min
Moderate:
Contraindicated if CrCl < 60 mL/min
Severe:
Contraindicated if CrCl < 60 mL/min
Dialysis:
Contraindicated. Ineffective and may increase toxicity.
Hepatic Impairment:
Mild:
No specific dosage adjustment provided; use with caution.
Moderate:
No specific dosage adjustment provided; use with caution.
Severe:
No specific dosage adjustment provided; use with caution. Monitor for signs of hepatotoxicity.
Pharmacology
Mechanism of Action
Nitrofurantoin is reduced by bacterial flavoproteins to reactive intermediates that inactivate or alter bacterial ribosomal proteins, DNA, RNA, and other metabolic enzymes. This leads to inhibition of bacterial cell wall synthesis, protein synthesis, aerobic energy metabolism, and DNA/RNA synthesis. The broad spectrum of activity is due to multiple sites of action, which also minimizes the development of bacterial resistance.
Pharmacokinetics
Absorption:
Bioavailability:
Well absorbed (increased with food)
Tmax:
Approximately 4 hours
FoodEffect:
Food significantly increases the bioavailability and plasma concentrations of nitrofurantoin macrocrystals/monohydrate, and prolongs its duration of action. Macrobid should be taken with food.
Distribution:
Vd:
Not widely reported, primarily distributed to the urinary tract
ProteinBinding:
Approximately 60%
CnssPenetration:
Limited
Elimination:
HalfLife:
0.3 to 1 hour
Clearance:
Rapid renal excretion
ExcretionRoute:
Primarily renal (glomerular filtration and tubular secretion)
Unchanged:
20-50% of the dose is excreted unchanged in the urine
Pharmacodynamics
OnsetOfAction:
Within hours (urinary concentrations achieved rapidly)
PeakEffect:
Not precisely defined for clinical effect, but peak urinary concentrations within 2-4 hours
DurationOfAction:
Approximately 6-8 hours (due to rapid excretion)
Safety & Warnings
Side Effects
Serious Side Effects: Seek Medical Help Immediately
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you experience any of the following symptoms, contact your doctor or seek medical attention right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Rarely, allergic reactions can be fatal.
Signs of pancreatitis (pancreas problem), such as:
+ Severe stomach pain
+ Severe back pain
+ Severe upset stomach or vomiting
Signs of lupus, such as:
+ Rash on the cheeks or other body parts
+ Easy sunburn
+ Muscle or joint pain
+ Chest pain or shortness of breath
+ Swelling in the arms or legs
Inability to control eye movements
Diarrhea, especially if it is severe, bloody, or watery (may be a sign of C. diff-associated diarrhea, a potentially life-threatening condition)
Liver problems, such as:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Nerve problems, such as:
+ Burning sensation
+ Numbness
+ Tingling
+ Abnormal sensations (especially if you have kidney problems, anemia, diabetes, electrolyte problems, or low vitamin B levels)
Other Side Effects
Most people experience few or no side effects. However, if you experience any of the following side effects, contact your doctor or seek medical attention if they bother you or do not go away:
Headache
Upset stomach or vomiting
Decreased appetite
Stomach pain or diarrhea
Dizziness, drowsiness, tiredness, or weakness
Hair loss (usually reversible after stopping the medication)
* Urine color change to brown (harmless and temporary)
Reporting Side Effects
If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you experience any of the following symptoms, contact your doctor or seek medical attention right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Rarely, allergic reactions can be fatal.
Signs of pancreatitis (pancreas problem), such as:
+ Severe stomach pain
+ Severe back pain
+ Severe upset stomach or vomiting
Signs of lupus, such as:
+ Rash on the cheeks or other body parts
+ Easy sunburn
+ Muscle or joint pain
+ Chest pain or shortness of breath
+ Swelling in the arms or legs
Inability to control eye movements
Diarrhea, especially if it is severe, bloody, or watery (may be a sign of C. diff-associated diarrhea, a potentially life-threatening condition)
Liver problems, such as:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Nerve problems, such as:
+ Burning sensation
+ Numbness
+ Tingling
+ Abnormal sensations (especially if you have kidney problems, anemia, diabetes, electrolyte problems, or low vitamin B levels)
Other Side Effects
Most people experience few or no side effects. However, if you experience any of the following side effects, contact your doctor or seek medical attention if they bother you or do not go away:
Headache
Upset stomach or vomiting
Decreased appetite
Stomach pain or diarrhea
Dizziness, drowsiness, tiredness, or weakness
Hair loss (usually reversible after stopping the medication)
* Urine color change to brown (harmless and temporary)
Reporting Side Effects
If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Numbness, tingling, or weakness in hands or feet (signs of peripheral neuropathy)
- Persistent cough, difficulty breathing, chest pain, or fever (signs of lung problems)
- Unusual tiredness, yellowing of skin or eyes, dark urine, nausea, vomiting, or stomach pain (signs of liver problems)
- Severe diarrhea (watery or bloody) that does not stop (signs of C. difficile infection)
- Signs of allergic reaction (rash, itching, swelling, severe dizziness, trouble breathing)
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following conditions to ensure safe treatment:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Describe the allergic reactions you have experienced.
Kidney disease, as it may affect how your body processes the medication.
Difficulty urinating, as this may be a sign of an underlying condition that could interact with the medication.
Previous liver problems caused by this medication, as this may increase the risk of further liver damage.
Pregnancy, particularly if you are 38 weeks or more pregnant, as the medication may affect the fetus.
Special Considerations for Children:
If the patient is a child under 1 month of age, do not administer this medication, as it is not suitable for infants at this age.
Additional Precautions:
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health conditions with your doctor and pharmacist to ensure safe treatment.
Do not start, stop, or change the dosage of any medication without consulting your doctor to avoid potential interactions or adverse effects.
It is essential to inform your doctor about the following conditions to ensure safe treatment:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Describe the allergic reactions you have experienced.
Kidney disease, as it may affect how your body processes the medication.
Difficulty urinating, as this may be a sign of an underlying condition that could interact with the medication.
Previous liver problems caused by this medication, as this may increase the risk of further liver damage.
Pregnancy, particularly if you are 38 weeks or more pregnant, as the medication may affect the fetus.
Special Considerations for Children:
If the patient is a child under 1 month of age, do not administer this medication, as it is not suitable for infants at this age.
Additional Precautions:
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health conditions with your doctor and pharmacist to ensure safe treatment.
Do not start, stop, or change the dosage of any medication without consulting your doctor to avoid potential interactions or adverse effects.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
If you have a deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD), you may be at a higher risk of developing anemia. Individuals of African, South Asian, Middle Eastern, and Mediterranean descent are more likely to have low G6PD levels.
If you have diabetes and regularly test your urine for glucose, consult with your doctor to determine the most suitable testing methods for you.
Do not take this medication for a longer duration than prescribed. Prolonged use may increase the risk of a second infection.
Although rare, this medication can cause severe and potentially life-threatening lung problems, particularly in individuals who have been taking it for 6 months or longer. These lung problems can occur without warning signs. If you are taking this medication long-term, your doctor will monitor your lung function. Immediately contact your doctor if you experience symptoms such as fever, chills, chest pain, an abnormal cough, difficulty breathing, or other respiratory problems.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or breastfeeding, discuss the potential benefits and risks of this medication with your doctor to ensure the best outcome for you and your baby.
If you have a deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD), you may be at a higher risk of developing anemia. Individuals of African, South Asian, Middle Eastern, and Mediterranean descent are more likely to have low G6PD levels.
If you have diabetes and regularly test your urine for glucose, consult with your doctor to determine the most suitable testing methods for you.
Do not take this medication for a longer duration than prescribed. Prolonged use may increase the risk of a second infection.
Although rare, this medication can cause severe and potentially life-threatening lung problems, particularly in individuals who have been taking it for 6 months or longer. These lung problems can occur without warning signs. If you are taking this medication long-term, your doctor will monitor your lung function. Immediately contact your doctor if you experience symptoms such as fever, chills, chest pain, an abnormal cough, difficulty breathing, or other respiratory problems.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or breastfeeding, discuss the potential benefits and risks of this medication with your doctor to ensure the best outcome for you and your baby.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Diarrhea
- Headache
- Dizziness
What to Do:
Seek immediate medical attention or call a poison control center (1-800-222-1222). There is no specific antidote; treatment is supportive.
Drug Interactions
Major Interactions
- Magnesium trisilicate-containing antacids (decreased absorption of nitrofurantoin)
- Probenecid (decreased renal excretion of nitrofurantoin, increased toxicity)
- Sulfinpyrazone (decreased renal excretion of nitrofurantoin, increased toxicity)
Moderate Interactions
- Live bacterial vaccines (e.g., Typhoid vaccine - may reduce therapeutic effect of vaccine)
- Quinolone antibiotics (e.g., Ciprofloxacin, Levofloxacin - theoretical antagonism, though clinical significance for UTI is generally low)
Monitoring
Baseline Monitoring
Renal function (CrCl)
Rationale: Nitrofurantoin is contraindicated in patients with CrCl < 60 mL/min due to reduced efficacy and increased risk of toxicity.
Timing: Prior to initiation of therapy
Liver function tests (ALT, AST, bilirubin)
Rationale: To establish baseline, especially in patients with pre-existing liver disease or history of liver injury.
Timing: Prior to initiation of therapy (if clinically indicated)
Routine Monitoring
Renal function (CrCl)
Frequency: Periodically, especially during prolonged therapy or in elderly patients
Target: > 60 mL/min
Action Threshold: Discontinue if CrCl falls below 60 mL/min
Pulmonary function tests
Frequency: If long-term therapy is anticipated or if respiratory symptoms develop
Target: Normal
Action Threshold: Discontinue if signs of pulmonary toxicity (e.g., persistent cough, dyspnea, infiltrates on chest X-ray) develop
Liver function tests (ALT, AST, bilirubin)
Frequency: Periodically during prolonged therapy or if symptoms of liver injury develop
Target: Normal
Action Threshold: Discontinue if significant elevations or signs of hepatotoxicity develop
Symptom Monitoring
- Signs of peripheral neuropathy (e.g., tingling, numbness, weakness in extremities)
- Signs of pulmonary toxicity (e.g., persistent cough, dyspnea, chest pain, fever)
- Signs of hepatotoxicity (e.g., fatigue, nausea, vomiting, dark urine, jaundice, abdominal pain)
- Signs of C. difficile-associated diarrhea (e.g., severe diarrhea, abdominal cramps, fever)
- Signs of hemolytic anemia (e.g., pallor, fatigue, dark urine, jaundice)
Special Patient Groups
Pregnancy
Generally considered safe for use during the first and second trimesters for UTI treatment. However, it is contraindicated at term (38-42 weeks gestation) due to the risk of hemolytic anemia in the neonate, especially in infants with immature enzyme systems or G6PD deficiency.
Trimester-Specific Risks:
First Trimester:
Low risk, generally considered safe for short-term use.
Second Trimester:
Low risk, generally considered safe for short-term use.
Third Trimester:
Contraindicated at term (38-42 weeks gestation) due to risk of neonatal hemolytic anemia.
Lactation
Considered compatible with breastfeeding (L2). Small amounts are excreted into breast milk. Use with caution in infants with G6PD deficiency or those less than 1 month of age due to theoretical risk of hemolytic anemia.
Infant Risk:
Low risk for most infants. Potential risk of hemolytic anemia in G6PD deficient infants or neonates.
Pediatric Use
Contraindicated in infants less than 1 month of age due to the risk of hemolytic anemia. Macrobid 100mg capsules are generally not recommended for children under 12 years of age due to the dosage form.
Geriatric Use
Increased risk of pulmonary, hepatic, and neurological toxicities (especially peripheral neuropathy) due to age-related decline in renal function. Use with caution and monitor renal function closely. Contraindicated if CrCl < 60 mL/min.
Clinical Information
Clinical Pearls
- Always take Macrobid with food to enhance absorption and minimize gastrointestinal upset.
- Inform patients that their urine may turn dark yellow or brown, which is a harmless side effect.
- Emphasize the importance of completing the full course of therapy, even if symptoms improve, to prevent recurrence and resistance.
- Counsel patients on the signs and symptoms of serious adverse effects, particularly pulmonary toxicity and peripheral neuropathy, and advise them to seek medical attention if these occur.
- Nitrofurantoin is primarily effective for lower urinary tract infections and does not achieve therapeutic concentrations in systemic tissues.
Alternative Therapies
- Trimethoprim/sulfamethoxazole (Bactrim)
- Fosfomycin (Monurol)
- Pivmecillinam (not available in US)
- Fluoroquinolones (e.g., Ciprofloxacin, Levofloxacin - generally reserved for more complicated UTIs or when other options are not suitable due to resistance concerns)
- Beta-lactam antibiotics (e.g., Amoxicillin/clavulanate, Cephalexin - often less effective for uncomplicated UTIs due to resistance patterns)
Cost & Coverage
Average Cost:
Varies widely, typically $20-$100+ per 30 capsules
Generic Available:
Yes
Insurance Coverage:
Tier 1 or 2 (generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with additional patient information leaflets, so it's a good idea to check with your pharmacist for more details. If you have any questions or concerns about this medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider for guidance. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide information about the medication taken, the amount, and the time it happened, as this will help healthcare professionals provide the best possible care.