Nitrofurantoin vs. amoxicillin: What's the difference?

What are nitrofurantoin and amoxicillin?

Nitrofurantoin is an antibiotic specially used to treat urinary tract infections (UTIs) caused by a number of types of bacteria such as E. Coli, Enterococcus, Klebsiella, Enterobacter cystitis, and Staphylococcus aureus. It interferes with the production of bacterial proteins, DNA, and cell walls. Bacteria are unable to survive without a cell wall or to multiply without DNA. There are three forms of nitrofurantoin available: Furadantin, a microcrystalline form; Macrodantin, a macrocrystalline; and Macrobid, a sustained release form of macrocrystalline used twice daily. The macrocrystalline form is absorbed more slowly than the microcrystalline form and is useful for individuals who cannot tolerate the microcrystalline form.

Amoxicillin is a penicillin-type antibiotic, a drug class that also includes ampicillin (Unasyn), piperacillin (Pipracil), ticarcillin (Ticar), and others. Penicillin-type antibiotics all do not directly kill bacteria, but they stop bacteria from multiplying by preventing them from forming the walls that surround them. Bacteria cannot survive without a cell wall, which protects the bacteria from their environment and keeps the contents of the bacterial cell together. Amoxicillin is effective against many different bacteria including H. influenzae, N. gonorrhoea, E. coli, Pneumococci, Streptococci, and certain strains of Staphylococci. Amoxicillin is used to treat infections of the middle ear, tonsils, throat, larynx (laryngitis), bronchi (bronchitis), lungs (pneumonia), urinary tract, and skin. It is also used to treat gonorrhea.

What are the side effects of nitrofurantoin and amoxicillin?

Nitrofurantoin

Common side effects of nitrofurantoin include:

The macrocrystalline form (Macrodantin) appears to cause less stomach upset. Stomach upset also can be minimized by using a lower dose or by taking nitrofurantoin with food or milk.

Possible serious side effects include:

Nitrofurantoin can cause serious lung injury. The reaction can occur within hours of the start of treatment if the patient has previously received nitrofurantoin, or within a few days of starting nitrofurantoin for the first time. Symptoms include:

In other persons, lung injury may occur after approximately a month of treatment. Symptoms include:

  • Difficulty breathing
  • Rapid breathing
  • Cough

Fortunately, the symptoms usually resolve within a week if the medication is stopped. In other individuals, lung injury may not develop until after several months or years of therapy. Unless it is recognized and treated, this delayed lung injury can result in permanent lung damage that remains even after the drug is stopped.

Nitrofurantoin can also cause damage to the sensory nerves of the arms and legs (peripheral neuropathy), which can cause tingling in the extremities. The condition can become severe and is more likely to occur in people with diabetes, vitamin B deficiency, or general debilitation.

Reduced red blood cell count (anemia) by breaking red blood cells (hemolytic anemia) can occur from nitrofurantoin. This reaction occurs most frequently in persons with a deficiency of an enzyme called glucose-6-phosphate dehydrogenase that is very important to the survival of red blood cells.

Nitrofurantoin also can cause liver damage leading to jaundice or a form of hepatitis that can be fatal. Elevated liver enzymes indicate liver damage and are a reason to stop the drug.

Treatment with nitrofurantoin can cause urine to change color to a dark yellow or brown.

Amoxicillin

Side effects due to amoxicillin include:

People who are allergic to the cephalosporin class of antibiotics, which are related to the penicillins, for example, cefaclor (Ceclor), cephalexin (Keflex), and cefprozil (Cefzil), may or may not be allergic to penicillins.

Serious but rare reactions include:

Amoxicillin can alter the normal bacteria in the colon and encourage overgrowth of some bacteria such as Clostridium difficile, which causes inflammation of the colon (pseudomembranous colitis). Patients who develop signs of pseudomembranous colitis after starting amoxicillin (diarrhea, fever, abdominal pain, and possibly shock) should contact their doctor immediately.

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What is the dosage of nitrofurantoin vs. amoxicillin?

Nitrofurantoin

  • The recommended adult dose for treating urinary tract infections is 50-100 mg 4 times daily (Macrodantin, Furadantin) or 100 mg every 12 hours (Macrobid) for 7 days or for 3 days after obtaining sterile urine.
  • Nitrofurantoin can be taken with or without meals. Taking it with meals increases its absorption into the body.
  • The suspension can be mixed with water, milk, juice, or infant formula.
  • It also is used once a day (or in some children, twice daily) to prevent urinary tract infections.
  • It should not be used in persons with poor kidney function.

Amoxicillin

  • For most infections in adults, the dose of amoxicillin is 250 mg every 8 hours, 500 mg every 8 hours, 500 mg every 12 hours or 875 mg every 12 hours, depending on the type and severity of infection.
  • For the treatment of adults with gonorrhea, the dose is 3 g given as one dose.
  • For most infections, children older than 3 months but less than 40 kg are treated with 25 or 45 mg/kg/day in divided doses every 12 hours or 20 or 40 mg/kg/day with one-third of the daily dose given every 8 hours depending on the type and severity of the infection.
  • Amoxicillin can be taken with or without food.

What drugs interact with nitrofurantoin and amoxicillin?

Nitrofurantoin

  • High doses of probenecid (Benemid) or sulfinpyrazone (Anturane) can partially block the kidneys' elimination of nitrofurantoin. This can increase the blood concentrations of nitrofurantoin and the risk of toxicity from nitrofurantoin.
  • Concomitant administration of a magnesium trisilicate antacid may decrease the absorption of nitrofurantoin, reducing the effectiveness of nitrofurantoin.
  • Nitrofurantoin may reduce the activity of live tuberculosis vaccine (BCG vaccine) and live typhoid vaccine. In laboratory tests, nitrofurantoin reduced the effect of quinolone antibiotics, for example, norfloxacin (Noroxin). Therefore, nitrofurantoin should not be combined with quinolone antibiotics.

Amoxicillin

Amoxicillin is rarely associated with important drug interactions.

Are nitrofurantoin and amoxicillin safe to use while pregnant or breastfeeding?

Nitrofurantoin

Although there are no adequate studies of nitrofurantoin in pregnant women, many women have safely used it during pregnancy. However, nitrofurantoin should not be used near the time of delivery (38-42 weeks gestation) since it interferes with the immature enzyme systems in the red blood cells of newborns, damaging the cells and resulting in anemia.

Nitrofurantoin is distributed into breast milk and should be used with caution in women who are breastfeeding.

Amoxicillin

Penicillins are generally considered safe for use by pregnant women who are not allergic to penicillin.

Small amounts of amoxicillin may be excreted in breast milk and may cause diarrhea or allergic responses in nursing infants. Amoxicillin is generally considered safe to use while breastfeeding. Amoxicillin is used to treat infections in the newborn.

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Summary

Nitrofurantoin and amoxicillin are antibiotics used to treat urinary tract infections (UTIs). Amoxicillin is also used to treat bacterial infections of the middle ear, tonsils, throat, larynx (laryngitis), bronchi (bronchitis), lungs (pneumonia), and skin. It is also used to treat gonorrhea.

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Medically Reviewed on 6/27/2019
References
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