Macrobid (Nitrofurantoin Macrocrystals)

(℞) Prescription Required

Macrobid (Nitrofurantoin Macrocrystals) Dosage and Side Effects

MACROBID is an antibiotic used to treat or prevent urinary tract infections. MACROBID works by killing the bacteria that cause the infection or by preventing the bacteria from growing.

Warnings and Precautions

In 2009, the FDA approved a label change for MACROBID, adding a warning that the drug should not be taken by those who had jaundice (a yellowing of the skin) or liver problems.

You shouldn’t take MACROBID if you have severe kidney problems or have trouble passing urine.

If you take MACROBID for six months or longer, your doctor should monitor you closely for any potential lung problems, because the drug has been linked to pulmonary fibrosis, a scarring disease of the lungs

Pregnancy and MACROBID

The FDA classifies MACROBID as a Pregnancy Category B drug. That means that animal studies have not found evidence of harm to the developing fetus, though no adequate studies have been done in pregnant women.

For that reason, the drug should be used during pregnancy only if the benefits outweigh the potential risks.

If you are breastfeeding, research suggests that MACROBID poses minimal risk to the infant. Talk to your doctor about breastfeeding while on MACROBID.

Infants under one month of age should not be given MACROBID.

Side Effects

Common Side Effects of MACROBID

Diarrhea, gas, nausea, and headache are common side effects. These usually do not need medical attention. However, if they are severe, check in with your doctor.

Severe Side Effects of MACROBID

If you have any of these symptoms while taking MACROBID, check with your doctor right away. Some of them could indicate liver problems.

  • Stomach pain, tenderness
  • Stools the color of clay or urine that is dark
  • No appetite or lower appetite
  • Nausea, vomiting
  • Yellowing of skin, eyes
  • Weakness, fatigue
  • Feet or leg swelling

Other side effects that warrant an immediate call to the doctor include:

  • Chills, cough, fever
  • Hives, itching, shortness of breath, skin rash
  • Pain in joints or muscles

Rare Side Effects of MACROBID

Some of the rare side effects of MACROBID are:

  • Confusion
  • Light-colored stools
  • Color blindness
  • Vomiting blood
  • Scaly skin

Proper Use of this medication

The recommended dose of MACROBID is different depending on whether it is being used to treat a urinary tract infection or prevent one.

In general, here are the ranges of oral doses given:

  • 50 to 100 milligrams (mg) at bedtime for adults and teens to prevent infections.
  • 50 to 100 mg every six hours for adults and teens to treat infections.
  • Doses are based on body weight for children and infants one month and older.
  • For the extended-release capsules, 100 mg every 12 hours for 7 days for adults, teens and children ages 12 and older. The dose is individualized for children under age 12.


Overdosing on MACROBID can cause vomiting. Call your doctor if you think you have taken too much MACROBID.

Missed Dose of MACROBID

Take a missed dose of MACROBID as soon as possible when you remember. However, if it is nearly time for your next dose, resume your regular schedule. Don't double up on doses.

Interactions with this medication

If you are taking MACROBID, avoid antacids that contain magnesium trisilicate. Taking both together will reduce how well and how quickly the antibiotic is absorbed.

Taking MACROBID while you are on the antifungal drug Diflucan (fluconazole) is not recommended. If it is necessary, your doctor may change the dose of each medicine or how often you take them.

Tell your doctor if you are on Probalan (probenecid) or Anturane (sulfinpyrazone), used to treat gout. They can affect the way the MACROBID works.

If you have diabetes while taking MACROBID, you may have a false-positive result on urine tests.

You should always tell your doctor about any prescription, non-prescription, over-the-counter (OTC), illegal and recreational drugs, herbal remedies, nutritional and dietary supplements, and all other drugs and treatments you’re taking.

MACROBID and Alcohol

Your doctor may tell you to avoid alcohol while on MACROBID. Combining alcohol and MACROBID can intensify any side effects

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The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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