Nitrofurantoin

About Nitrofurantoin

Nitrofurantoin kills bacteria that cause urinary infections; it is highly soluble in urine, and the Macrobid label notes that it lacks the broader tissue distribution of other drugs approved for urinary tract infections. Like other antibiotics, it does not treat viral infections such as the common cold. Macrobid is labeled only for acute uncomplicated urinary tract infections (acute cystitis) caused by susceptible Escherichia coli or Staphylococcus saprophyticus, in adults and children over 12, as one 100 mg capsule every 12 hours with food for 7 days. Macrocrystal capsules and the suspension are labeled for urinary tract infections caused by susceptible bacteria from 1 month of age: adults take 50 to 100 mg four times a day and children 5 to 7 mg/kg a day in four doses, for one week or at least 3 days after the urine becomes sterile. Their labels add that lower doses (in adults, 50 to 100 mg at bedtime) may be adequate for long-term suppressive therapy. No form is indicated for pyelonephritis or perinephric abscesses.

There is no boxed warning. Acute, subacute and chronic lung reactions have occurred; chronic reactions are rare and generally follow six months or more of therapy, so people on long-term treatment have their lungs closely monitored, and the drug is stopped if a reaction appears. Rare liver reactions, from hepatitis to hepatic necrosis, call for periodic liver tests, and peripheral neuropathy can become severe or irreversible; kidney impairment, anemia, diabetes, electrolyte imbalance, vitamin B deficiency and debilitating disease may make it more likely. Optic neuritis, hemolytic anemia in people with G6PD deficiency, serious allergic reactions and Clostridioides difficile diarrhea have also been reported. It must not be taken with anuria, oliguria or significant kidney impairment (creatinine clearance under 60 mL per minute or a clinically significant raised serum creatinine), after cholestatic jaundice or liver problems from nitrofurantoin, at term in pregnancy (38 to 42 weeks), during labor and delivery, or by infants under 1 month. Nausea, headache and flatulence were the most frequent side effects with Macrobid.

Nitrofurantoin may turn urine brown. The Furadantin label says breastfeeding is not recommended for infants under 1 month or with G6PD deficiency, who are at risk of hemolytic anemia; the Macrobid label asks for a choice between nursing and the drug for infants under 1 month. Macrodantin capsules are listed as discontinued, and generic macrocrystal capsules come in 25, 50 and 100 mg. Furadantin suspension is still listed in 25 and 50 mg per 5 mL, and generic 25 mg per 5 mL suspension comes from several makers; Furadantin tablets and Furalan are no longer on the market.

Taking Nitrofurantoin

How to take it

With food, which improves absorption and tolerance; the Macrobid label suggests breakfast and dinner. Shake the suspension vigorously before each dose and measure it with an oral dosing syringe. Finish the course even if you feel better.

If you miss a dose

Take it as soon as you remember. If it is almost time for the next dose, skip the missed dose and space any remaining doses for that day evenly. Do not take a double dose.

Storage

Capsules at room temperature in a tightly closed container, away from excess heat and moisture. Keep the suspension at room temperature, away from strong light, which can darken it, and do not freeze it; the Furadantin label says to discard any left 30 days after first opening.

Interactions to know about

Antacids containing magnesium trisilicate reduce its absorption, and probenecid and sulfinpyrazone can inhibit its secretion by the kidneys. It can cause false-positive urine glucose results with Benedict’s or Fehling’s solution, though not with enzymatic glucose tests.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Nitrofurantoin differs from pharmacy to pharmacy

The two capsule types are different products: a pharmacist fills monohydrate/macrocrystals (twice a day) or macrocrystals (four times a day) as written and substitutes only a generic rated to the product prescribed. Both have several generic makers, so quotes for the same course differ by each pharmacy’s dispensing fee and markup and by whether nitrofurantoin is on its flat-price generic list.

A four-times-a-day course uses more capsules than a twice-a-day course, and long-term suppressive therapy is quoted on the supply written. The suspension is quoted by bottle, and Furadantin’s 50 mg per 5 mL strength has no rated generic.

Ways to pay less for Nitrofurantoin without insurance

• Ask whether nitrofurantoin is on the pharmacy’s flat-price generic list, and compare more than one pharmacy.
• If the prescription names Macrobid, check that it allows a rated generic.
• For a child’s suspension, ask how many bottles the full course needs, so the quote covers all of it.
• For long-term suppressive therapy, ask the prescriber whether a ninety-day supply is appropriate.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Nitrofurantoin

1. 1.Is my kidney function good enough for nitrofurantoin?
2. 2.Should I take my doses with breakfast and dinner?
3. 3.Which cough, breathing, numbness or liver symptoms mean I should stop and call?
4. 4.Can I keep using my antacid while I take it?

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