Nitrofurantoin vs. Bactrim

• Nitrofurantoin and Bactrim (sulfamethoxazole and trimethoprim) are antibiotics used to treat urinary tract infections (UTIs).
• Bactrim is also used to treat other types of bacterial infections including flares of chronic bronchitis due to bacteria, middle ear infections, for prevention of infections due to pneumococcus in organ transplant recipients, for the treatment or prevention of Pneumocystis carinii pneumonia, chancroid, and for prevention of Toxoplasma encephalitis in patients with AIDS.
• Brand names of nitrofurantoin include Macrobid, Macrodantin, and Furadantin.
• Side effects of nitrofurantoin and Bactrim that are similar include headache, rash, nausea, vomiting, loss of appetite, and diarrhea.
• Side effects of nitrofurantoin that are different from Bactrim include itching, change in urine color, and abdominal pain.
• Side effects of Bactrim that are different from nitrofurantoin include dizziness and lethargy.

Nitrofurantoin is an antibiotic used to treat urinary tract infections (UTIs) caused by several types of bacteria including E. Coli, Enterobacter cystitis, Enterococcus, Klebsiella, and Staphylococcus aureus. Nitrofurantoin interferes with the production of bacterial proteins, DNA, and cell walls. Bacteria cannot survive without a cell wall or multiply without DNA. Three forms of nitrofurantoin are available: 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 useful for patients who cannot tolerate the microcrystalline form.

Bactrim (sulfamethoxazole and trimethoprim) is a combination of an antibacterial sulfonamide (a "sulfa" drug) and a folic acid inhibitor. By combining both drugs, two important steps required in the production of bacterial proteins are interrupted, and the combination is more effective than either drug alone. Bactrim is used to treat bacterial infections including urinary tract infections, flares of chronic bronchitis due to bacteria, middle ear infections, for prevention of infections due to pneumococcus in organ transplant recipients, for the treatment or prevention of Pneumocystis carinii pneumonia, chancroid, and prevention of Toxoplasma encephalitis in patients with AIDS.

Nitrofurantoin

Common side effects of nitrofurantoin include:

• Headache
• Rash
• Itching
• Nausea
• Vomiting
• Change in urine color
• Loss of appetite
• Diarrhea
• Abdominal pain

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:

• Lung injury
• Anemia
• Liver damage
• Exfoliative dermatitis
• Clostridium difficile colitis
• Vasculitis

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:

• Difficulty breathing
• Chills
• Fever
• Chest pain
• Cough

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.

Bactrim

Common side effects of sulfamethoxazole/trimethoprim are:

• Dizziness
• Headache
• Lethargy
• Diarrhea
• Anorexia
• Nausea
• Vomiting
• Rash

Other side effects include:

• Liver damage
• Low white blood cell count
• Low platelet count (thrombocytopenia)
• Anemia

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.

Bactrim

• The recommended adult dose for urinary tract infections is one double strength tablet (Bactrim DS, Septra DS) or two single strength tablets every 12 hours for 10 to 14 days.
• Flares of chronic bronchitis are treated with a similar regimen for 14 days.
• Bactrim should be taken with 6 to 8 ounces of liquid to prevent crystals from forming in the urine. Persons with advanced kidney disease may require lower doses.

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.

Bactrim

Bactrim (sulfamethoxazole/trimethoprim) can enhance the blood-thinning effects of warfarin (Coumadin, Jantoven), possibly leading to bleeding.

Sulfonamides such as sulfamethoxazole can increase the metabolism (breakdown and elimination) of cyclosporine (causing loss of effectiveness of cyclosporine), and can add to the kidney damage caused by cyclosporine.

All sulfonamides can crystallize in urine when the urine is acidic. Since methenamine (Hiprex, Urex, Mandelamine) causes acidic urine, it should not be used with sulfonamides.

Blood levels of phenytoin (Dilantin) may be increased by treatment with Bactrim. This may lead to side effects associated with phenytoin (Dilantin, Dilantin-125) such as dizziness, and reduced attention.

Bactrim also may increase blood levels of digoxin (Lanoxin) and possibly lead to serious toxic effects.

Anemia, due to a reduction in folic acid, can occur in persons receiving Bactrim in combination with:

• divalproex,
• valproic acid (Depakote, Depakote ER, Depakene, Depacon, Stavzor),
• methotrexate (Rheumatrex, Trexall),
• pyrimethamine,
• triamterene, or
• trimetrexate.

Increased blood levels of potassium may occur when Bactrim is combined with ACE inhibitors.

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 newborns' red blood cells, damaging the cells and resulting in anemia.

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

Bactrim

Use of sulfonamides may cause bilirubin to be displaced from proteins in the infant's blood. Displacement of bilirubin can lead to jaundice and a dangerous condition called kernicterus in the infant. For this reason, Bactrim should not be used near term (late in pregnancy) among women.

Bactrim should not be used by nursing mothers because sulfamethoxazole is excreted in breast milk and can cause kernicterus.