Nitrofurantoin
The usual first choice for an uncomplicated bladder infection, and a medicine whose label limits it to exactly that.
- Class
- Nitrofuran antibacterial
- Sold as
- Sold as: Macrobid, Macrodantin, Furadantin
- Prescription only
From the approved label
Nitrofurantoin
- Approved uses
- Nitrofurantoin capsules (monohydrate/macrocrystals) are indicated only for the treatment of acute uncomplicated urinary tract infections (acute cystitis) caused by susceptible strains of Escherichia coli or Staphylococcus saprophyticus.
- To reduce the development of drug-resistant bacteria and maintain the effectiveness of nitrofurantoin capsules (monohydrate/macrocrystals) and other antibacterial drugs, nitrofurantoin capsules (monohydrate/macrocrystals) should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria.
- When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy.
- Nitrofurantoin is not indicated for the treatment of pyelonephritis or perinephric abscesses.
- Forms and strengths
- Nitrofurantoin Capsules USP (monohydrate/macrocrystals), 100 mg are opaque black and opaque yellow size '0' hard gelatin capsule imprinted with 'Z' on cap and '66' on body with grey ink.
- How it is taken
- Nitrofurantoin capsules (monohydrate/macrocrystals) should be taken with food.
- Adults and Pediatric Patients Over 12 Years: One 100 mg capsule every 12 hours for seven days.
- Must not be used when
- Anuria, oliguria, or significant impairment of renal function (creatinine clearance under 60 mL per minute or clinically significant elevated serum creatinine) are contraindications.
- Treatment of this type of patient carries an increased risk of toxicity because of impaired excretion of the drug.
- Because of the possibility of hemolytic anemia due to immature erythrocyte enzyme systems (glutathione instability), the drug is contraindicated in pregnant patients at term (38 to 42 weeks gestation), during labor and delivery, or when the onset of labor is imminent.
- For the same reason, the drug is contraindicated in neonates under one month of age.
- Interactions
- Antacids containing magnesium trisilicate, when administered concomitantly with nitrofurantoin, reduce both the rate and extent of absorption.
- The mechanism for this interaction probably is adsorption of nitrofurantoin onto the surface of magnesium trisilicate.
- Uricosuric drugs, such as probenecid and sulfinpyrazone, can inhibit renal tubular secretion of nitrofurantoin.
- The resulting increase in nitrofurantoin serum levels may increase toxicity, and the decreased urinary levels could lessen its efficacy as a urinary tract antibacterial.
- Warnings and precautions
- Pulmonary Reactions ACUTE, SUBACUTE, OR CHRONIC PULMONARY REACTIONS HAVE BEEN OBSERVED IN PATIENTS TREATED WITH NITROFURANTOIN.
- IF THESE REACTIONS OCCUR, NITROFURANTOIN (MONOHYDRATE/MACROCRYSTALS) SHOULD BE DISCONTINUED AND APPROPRIATE MEASURES TAKEN.
- REPORTS HAVE CITED PULMONARY REACTIONS AS A CONTRIBUTING CAUSE OF DEATH.
- CHRONIC PULMONARY REACTIONS (DIFFUSE INTERSTITIAL PNEUMONITIS OR PULMONARY FIBROSIS, OR BOTH) CAN DEVELOP INSIDIOUSLY.
- Common side effects
- In clinical trials of nitrofurantoin (monohydrate/macrocrystals), the most frequent clinical adverse events that were reported as possibly or probably drug-related were nausea (8%), headache (6%), and flatulence (1.5%).
- Pregnancy
- Teratogenic Effects Several reproduction studies have been performed in rabbits and rats at doses up to six times the human dose and have revealed no evidence of impaired fertility or harm to the fetus due to nitrofurantoin. In a single published study conducted in mice at 68 times the human dose (based on mg/kg administered to the dam), growth retardation and a low incidence of minor and common malformations were observed.
- How it acts
- Mechanism of Action The mechanism of the antimicrobial action of nitrofurantoin is unusual among antibacterials. Nitrofurantoin is reduced by bacterial flavoproteins to reactive intermediates which inactivate or alter bacterial ribosomal proteins and other macromolecules.
- Label holder:
- Aurobindo Pharma Limited
- Label version:
This section reports the approved product information. The wording is condensed from the regulator's own summary, and the full document is linked under Sources.
Written by us
How it works
Nitrofurantoin is concentrated in the urine rather than spread through the body, and that is both why it works in the bladder and why the label restricts it to the bladder. The same property explains the contraindication tied to reduced kidney function: if the medicine is not delivered into the urine in sufficient quantity, it is not doing the job the label describes.
Original and generic
Off patent and dispensed as a generic almost everywhere. Macrobid and Macrodantin are brand names for different formulations of the same substance rather than different medicines.
What it costs
One of the cheapest courses in this catalogue, and in most European countries the medicine costs far less than the consultation that leads to it.
How to get it legally
Prescription only across Europe. An online consultation covers the common case well, and the label itself marks where that stops: it is approved for acute uncomplicated cystitis, not for a kidney infection, so fever or flank pain belongs in a consultation where someone can examine you.
Questions
- Why does the label say it is only for cystitis?
- Because the medicine concentrates in the urine and does not reach useful levels in tissue elsewhere. The label states the restriction in its first sentence, which is unusual and deliberate.
- Does kidney function matter?
- Yes, and it is in the contraindications rather than in the small print. Reduced kidney function is the reason the medicine may not work and may accumulate, and it is one of the questions any legitimate consultation will ask.
- What if symptoms do not settle?
- That is a reason to go back rather than to repeat the course. Symptoms that persist after treatment can mean a resistant organism or an infection that was never confined to the bladder.
Sources
- NITROFURANTOIN: prescribing informationDailyMed, US National Library of Medicine. Label version 18 December 2024
- Drugs@FDA: ANDA209225US Food and Drug Administration
In this category
- TrimethoprimA single ingredient tablet for uncomplicated urinary infection, and a medicine that is easy to confuse with the two ingredient combination sold under a different name.
- FosfomycinA single sachet dissolved in water, approved for uncomplicated cystitis in women and for nothing else in the label.