Nitrofurantoin vs. Cephalexin: What's the difference?

What are nitrofurantoin and cephalexin?

Nitrofurantoin is an antibiotic used for treating urinary tract infections (UTIs) caused by certain bacteria including E. Coli, Enterobacter cystitis, Klebsiella, Enterococcus, and Staphylococcus aureus. Nitrofurantoin affects the production of bacterial proteins, DNA, and cell walls. Bacteria cannot survive without a cell wall or multiply without DNA. Nitrofurantoin is available in three forms: Furadantin, a microcrystalline form; Macrodantin, a macrocrystalline; and Macrobid, a sustained release form of macrocrystalline used twice daily. The macrocrystalline form is more slowly absorbed than the microcrystalline form and is used in patients who are unable to tolerate the microcrystalline form.

Cephalexin is a cephalosporin antibiotic, similar to penicillin in action and side effects. They stop or slow the growth of bacterial cells by preventing bacteria from forming the cell wall that surrounds each cell. The cell wall protects bacteria from the external environment and keeps the contents of the cell together, and without a cell wall, bacteria are not able to survive. Bacteria that are susceptible to cephalexin include Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, E. coli, and others. Common infections cephalexin treats include middle ear infections (otitis media), tonsillitis, throat infections, laryngitis, bronchitis, pneumonia, urinary tract infections (UTIs), skin infections, and bone infections.

What are the side effects of nitrofurantoin and cephalexin?

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.

Cephalexin

The most common side effects of cephalexin are:

Individuals who are allergic to penicillin may also be allergic to cephalexin. Serious but rare reactions include seizures, severe allergic reactions (anaphylaxis), and low platelet or red blood cell count.

Cephalexin, like almost all antibiotics, may cause mild or severe cases of pseudomembranous colitis, a mild to severe inflammation of the colon. Antibiotics, including cephalexin, alter the types of bacteria in the colon and permit overgrowth of a bacterium called Clostridium difficile. Studies indicate that toxins produced by Clostridium difficile are a primary cause of pseudomembranous colitis.

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What is the dosage of nitrofurantoin vs. cephalexin?

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.

Cephalexin

  • The dose of cephalexin for adults is 1 to 4 grams in divided doses.
  • The usual adult dose is 250 mg every 6 hours.
  • Some infections may be treated with 500 mg every 12 hours.
  • Children are treated with 25-100 mg/kg/day in divided doses.
  • The dosing interval may be every 6 or 12 hours depending on the type and seriousness of the infection.

What drugs interact with nitrofurantoin and cephalexin?

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.

Cephalexin

Cephalexin may reduce the effect of BCG and typhoid vaccines. Cephalexin should not be combined with BCG or typhoid vaccine unless there are no other options.

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

Nitrofurantin

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.

Cephalexin

There are no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, cephalexin should only be used during pregnancy if clearly needed.

Cephalexin is excreted in breast milk. Cephalexin should be used with caution or stopped when breastfeeding.

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Summary

Nitrofurantoin and cephalexin are antibiotics used to treat urinary tract infections (UTIs). Cephalexin is also used to treat middle ear infections (otitis media), tonsillitis, throat infections, laryngitis, bronchitis, pneumonia, skin infections, and bone infections.

Treatment & Diagnosis

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Medically Reviewed on 6/28/2019
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