Nitrofurantoin (Macrobid) 101: Uses, Effectiveness, and Safety Tips

Urinary tract infections (UTIs) are the most common type of bacterial infection in women, affecting up to 60% of adult women. 86% of UTIs in women are classified as acute uncomplicated cystitis caused by the bacteria Escherichia coli. Nitrofurantoin is one of three antibiotics recommended for the first-line treatment of acute uncomplicated cystitis.

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What Is Nitrofurantoin (Macrobid)?

Nitrofurantoin is an antibiotic approved by the United States Food and Drug Administration (FDA) in 1953 to treat lower UTIs. It works at a cellular level by targeting and inhibiting bacterial enzymes involved in DNA, RNA, and protein synthesis required for bacterial survival.

Nitrofurantoin is effective against most gram-positive and gram-negative bacteria, including those most commonly responsible for causing infection within the urinary tract:

Escherichia coli
Enterococci
Klebsiella
Staphylococcus saprophyticus
Enterobacter

It has gained popularity in recent years in treating UTIs due to its lower rates of antibiotic resistance than other antibiotic agents, such as trimethoprim/sulfamethoxazole and fluoroquinolones. Additionally, nitrofurantoin is unique in that it maintains low serum concentrations, minimizing systemic side effects, and does not significantly disrupt the intestinal microbiome.

Difference Between Nitrofurantoin and Macrobid

Macrobid is a brand-name oral medication that contains nitrofurantoin as its active ingredient. It is FDA-approved to treat and prevent uncomplicated UTIs in adults and children at least 12 years old.

Macrobid is formulated to include two forms of nitrofurantoin: nitrofurantoin macrocrystals and nitrofurantoin monohydrate. The macrocrystals are large particles that slow the medication's absorption. Nitrofurantoin monohydrate creates a gel upon exposure to intestinal secretions, helping to delay the release of the medication.

Compared to Macrodantin, another brand form of the medication that only contains only nitrofurantoin macrocrystals, Macrobid is less likely to cause gastrointestinal side effects.

Uses of Nitrofurantoin and Macrobid

Nitrofurantoin is indicated for treating acute uncomplicated UTIs caused by susceptible bacteria. An uncomplicated UTI is an infection of the lower urinary tract – the bladder and the urethra – in an otherwise healthy individual with a normal, unobstructed urinary system.

Nitrofurantoin can also be prescribed for prophylactic (preventive) therapy in women who experience recurrent UTIs. A recurrent UTI is defined as two or more separate UTI episodes within six months or three or more within one year. Research has indicated that continuous prophylaxis for 6-12 months reduces the rate of UTIs during the treatment period.

Limitations and When It Shouldn't Be Used

Nitrofurantoin should not be used to treat:

Pyelonephritis: kidney infection
Perinephric Abscess: a collection of pus that develops around the kidney, typically resulting from a severe kidney infection or urinary tract obstruction

For safety concerns, nitrofurantoin should also never be prescribed to people with the following health conditions:

Renal impairment (creatinine clearance <60 mL/min or elevated serum creatinine)
Pregnant patients at 38-42 weeks gestation
During labor and delivery, or when the onset of labor is imminent
Neonates less than one-month-old
History of cholestatic jaundice or liver dysfunction associated with nitrofurantoin
Known allergy to nitrofurantoin

Dosage and Administration

Nitrofurantoin is available in several dosage forms and strengths:

Generic Nitrofurantoin: 25 mg, 50 mg, 100 mg capsules
Macrobid: 100 mg capsule
Macrodantin: 25 mg, 50 mg, 100 mg capsules
Furadantin: 25mg/5mL oral suspension

Dosing regimens (outlined below) vary based on the dosage form prescribed, the patient's age, and the purpose of treatment. For best results, nitrofurantoin should be taken with food. Always follow the dosing directions provided to you by your doctor.

Treating Acute Uncomplicated UTIs

Adult Dosage

Macrodantin and Its Generic Form: 50-100 mg four times daily for seven days
Macrobid and Its Generic Form: 100 mg twice daily for five days

Pediatric Dosage (12–17 Years)

Macrodantin and Its Generic Form: 5-7 mg/kg of body weight in four divided doses for seven days
Macrobid and Its Generic Form: 100 mg twice daily for seven days

UTI Prevention

Adult Dosage

50-100 mg once daily at bedtime

Pediatric Dosage

1 mg/kg of body weight one per day or divided into two doses daily

Side Effects and Precautions

Nitrofurantoin is generally well-tolerated. The most frequently reported side effects are:

Nausea
Headache
Gas
Diarrhea
Stomach pain
Vomiting
Loss of appetite

Rarer, more serious side effects can occur. Contact your doctor immediately if you experience any of the following symptoms:

Allergic Reactions: skin rash, itching, hives, swelling of the face, lips, tongue, or throat
Lung Inflammation: shortness of breath, cough, difficulty breathing, chest pain
Liver Inflammation: itching, yellowing of the skin or whites of the eyes, nausea, vomiting, dark urine, pale stools, loss of appetite
Nerve Damage: numbness and pain in the hands and feet
Red Blood Cell Damage (Hemolysis): fatigue, weakness, pale skin
Severe Diarrhea

Taking nitrofurantoin with certain medications is not recommended due to an increased risk of side effects and reduced efficacy of the medication:

Antacids containing magnesium trisilicate may reduce the absorption of nitrofurantoin
Probenecid and sulfinpyrazone can inhibit the renal excretion of nitrofurantoin; the increase in serum levels can increase toxicity, and the decreased urinary levels could lessen its efficacy as a urinary tract antibiotic.

This may not include all possible drug interactions. Patients should inform their healthcare providers about their medications and supplements to avoid harmful interactions.

Effectiveness and Alternatives to Nitrofurantoin

Nitrofurantoin is a reliable first-line treatment for uncomplicated UTIs, achieving high clinical cure rates of up to 92% when administered for five to seven days. Its efficacy is comparable to trimethoprim/sulfamethoxazole, ciprofloxacin, and amoxicillin.

When available, antibiotics for treating UTIs should be selected based on culture and susceptibility results; otherwise, empirical therapy should be chosen by considering local antibiotic resistance patterns, the effectiveness of the medication, and the potential risk of side effects.

According to the Infectious Diseases Society of America 2010 guidelines, trimethoprim/sulfamethoxazole and fosfomycin are the other two recommended first-line agents for treating uncomplicated UTIs. Fosfomycin may have slightly lower efficacy compared to other first-line options and is not widely available in the United States.

While effective, fluoroquinolone antibiotics are considered second-line antimicrobial options due to their higher risk of side effects and propensity to cultivate drug resistance.

Beta-lactam antibiotics are not recommended as a first-line therapy for treating UTIs because E. coli resistance rates exceed 20%.

FAQs on Nitrofurantoin and Macrobid

1. Is Macrobid Safe During Pregnancy?

Nitrofurantoin is generally considered safe during pregnancy, particularly in the first trimester. However, it is recommended to avoid taking it late in pregnancy (38-42 weeks gestation) due to reports of hemolytic anemia (the excessive breakdown of red blood cells) in newborns who were exposed to the medication late in pregnancy. Always consult your healthcare provider before using this medication during pregnancy.

2. Can I Drink Alcohol With Nitrofurantoin?

While there is no direct interaction between nitrofurantoin and alcohol, consuming alcohol may exacerbate UTI symptoms and increase your risk of dehydration, making it harder for the body to fight off infection. For this reason, it is advisable to limit alcohol intake while taking this medication to treat a UTI.

3. What Should I Do If I Miss a Dose?

If you miss a dose of nitrofurantoin, take it as soon as you remember. If it's close to the next dose, skip the missed dose. Do not take two doses at once to make up for the missed dose.

4. Can Nitrofurantoin Cause Antibiotic Resistance?

While bacteria can develop resistance to nitrofurantoin, this has not been a significant problem since the antibiotic's development in 1953. Nitrofurantoin's unique mechanism of action makes the development of bacterial resistance relatively uncommon.

To prevent antibiotic resistance, it's important to follow your doctor's dosing instructions carefully with any antibiotic, taking all prescribed doses and completing the entire course, even if you start feeling better before finishing the medication.

Buying Nitrofurantoin (Macrobid) - What You Need to Know

In the United States, nitrofurantoin is classified as a legend drug, which means it requires a prescription from a licensed healthcare provider. This prescription requirement is to ensure appropriate and safe usage, dosage, and monitoring of the medication.

Once prescribed, nitrofurantoin can be purchased at licensed local or online pharmacies. To ensure the authenticity and safety of your medication, purchase from reputable and verified pharmacies. Be cautious of buying antibiotics from unverified or international sources, as these may not meet safety and quality standards.

Generic vs. Brand Name - Cost Comparison

The cost of nitrofurantoin may vary depending on factors like insurance coverage, the pharmacy you use, and the dosage form of the medication.

Generic nitrofurantoin is generally more affordable than brand-name versions like Macrobid and Macrodantin. According to FDA regulations, generic medications must demonstrate bioequivalence to their brand-name counterparts, ensuring the same efficacy and safety profile. This makes generics a cost-effective alternative without compromising treatment effectiveness.

Consult with your healthcare provider or pharmacist to determine the most cost-effective option for you.

Expert Tips for Patients on Nitrofurantoin

If your doctor prescribes nitrofurantoin for a UTI, consider the following tips to enhance treatment effectiveness and minimize side effects:

In addition to antibiotics, preventing and treating UTIs involves a combination of lifestyle modifications and good hygiene practices:

Stay Hydrated: drinking plenty of water helps flush out bacteria from the urinary tract
Wipe Properly: always wipe from front to back to prevent bacterial transfer from the gastrointestinal to urinary tracts
Urinate After Intercourse: this helps eliminate bacteria introduced into the urethra during sexual activity
Avoid Irritants: limit the use of harsh soaps, douches, and feminine sprays

Maximizing the benefits of nitrofurantoin while minimizing its side effects can be achieved through:

Adhere to the Prescribed Dosage: Do not skip doses or discontinue prematurely
Take With Food: This enhances absorption and reduces gastrointestinal discomfort
Monitor Symptoms: Keep track of symptom improvement and any adverse effects

Contact your doctor if you experience:

Severe Side Effects: Such as difficulty breathing, persistent cough, or significant rash
No Improvement: Symptoms persist or worsen after completing the course
Signs of a Complicated UTI: Including high fever, flank pain, or nausea and vomiting