How does this medication work? What will it do for me?

Nitrofurantoin belongs to the class of medications called antibiotics. It is used to treat urinary tract infections or bladder infections caused by certain types of bacteria. It helps to eliminate the symptoms of urinary tract infections such as burning, pain, frequent urination, and a constant urge to urinate.

Your doctor may have suggested this medication for conditions other than the ones listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each opaque, black and yellow, hard shell gelatin capsule, imprinted "Macrobid" on the black portion and "Norwich Eaton" on the yellow portion, contains the equivalent of 100 mg of nitrofurantoin in the form of nitrofurantoin macrocrystals and nitrofurantoin monohydrate. Nonmedicinal ingredients: carbomer 934P, compressible sugar, corn starch, D&C Yellow No. 10, edible gray ink, FD&C Blue No. 1, FD&C Red No. 40, gelatin, lactose, magnesium stearate, povidone, talc, and titanium dioxide.

How should I use this medication?

The recommended dose of this medication for adults and children over 12 years old is 100 mg twice daily. Nitrofurantoin should be taken with food or milk to reduce the risk of stomach upset.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. Finish all of this medication, even if you start to feel better. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take nitrofurantoin if you:

  • are allergic to nitrofurantoin or any ingredients of the medication
  • have significantly reduced kidney function
  • are a pregnant woman in labour or a pregnant woman expecting to go into labour soon (i.e., close to your due date)

Do not give this medication to infants under one month of age.

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • gas
  • headache
  • nausea

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • confusion
  • hair loss
  • joint or muscle pain
  • mood swings, unusual thoughts, or unusual behavior
  • symptoms of liver problems (such as yellow eyes or skin, abdominal pain, pale stools, dark urine, itching, nausea, or fatigue)
  • symptoms of low white blood cells (such as fever and chills or frequent infections)
  • symptoms of low red blood cells (such as fatigue, weakness, decreased energy, or pale skin)
  • symptoms of nerve damage (such as tingling, burning, pain, or numbness in the arms and legs; or difficulty controlling the muscles in the arms or legs)
  • vision changes

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • symptoms of a lung reaction to the medication (such as fever, chills, cough, chest pain, or difficulty breathing)
  • symptoms of a serious skin reaction (such as a severe blistering skin rash that causes the skin to peel or fall off; fever; or bloodshot eyes)
  • symptoms of a severe allergic reaction (such as hives, difficulty breathing, and swelling of the face or throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Discoloration of urine: This medication may turn your urine a rust yellow or brown colour. This is a normal effect of the medication and is not a cause for concern.

Overgrowth of organisms: The use of this medication may cause an overgrowth of microorganisms not killed by the medication, with results such as yeast infections and resistant bacteria.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. Do not use this medication if you are in labour or expect to go into labour soon (i.e., you are close to your due date). If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking nitrofurantoin, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children under one month of age.

What other drugs could interact with this medication?

There may be an interaction between nitrofurantoin and any of the following:

  • antacids containing magnesium
  • bacillus Calmette-Guerin (BCG)
  • probenecid
  • quinolone antibiotics (e.g., ciprofloxacin, norfloxacin)
  • sulfinpyrazone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.