Macrobid vs. Keflex for Urinary Tract Infection: Important Differences and Potential Risks.

Key takeaways

Nitrofurantoin (Macrobid) and cephalexin (Keflex) are both antibiotics, but they belong to different classes and treat infections differently. Nitrofurantoin is a nitrofuran antibiotic primarily used to treat or prevent urinary tract infections (UTIs) by targeting bacteria in the urinary tract. Cephalexin, a cephalosporin antibiotic, treats a broader range of infections, including UTIs, respiratory tract infections, ear infections, and skin infections, by preventing bacteria from forming protective coverings. Nitrofurantoin is typically taken with food to improve absorption and reduce stomach upset, while cephalexin can be taken with or without food. Nitrofurantoin is not recommended for use in the last weeks of pregnancy, whereas cephalexin is generally considered safe during pregnancy. Both medications are available in generic forms, making them more affordable. However, nitrofurantoin is not suitable for people with severe kidney problems, while cephalexin may not be recommended for those with severe allergies to penicillin or other cephalosporin antibiotics.

Nitrofurantoin

(Macrobid)

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Cephalexin

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Summary for Macrobid

Prescription only

Nitrofurantoin (Macrobid) is an antibiotic used to treat or prevent a urinary tract infection (UTI). Some side effects include nausea, headache, and gas. It can also make your urine turn dark yellow or brown. Nitrofurantoin (Macrobid) doesn't have many interactions with other medications. There's a lower-cost generic version of nitrofurantoin (Macrobid) available.

Indications for Macrobid

Treatment or prevention of urinary tract infections

Pros and Cons for Macrobid

Pros

Works well to treat and prevent UTIs
Available as both a capsule and a flavored oral suspension
Safe to take if you're allergic to other antibiotics like penicillin or sulfa medications (e.g., Bactrim, Septra (sulfamethoxazole / trimethoprim))

Cons

Might need to take up to four times a day (depending on the formulation)
Can interact with certain types of antacids, travel vaccines, and lab tests
Can harm your lungs, liver, and nerves if taken for a long period of time

Common Side Effects for Macrobid

Nausea (8%)
Headache (6%)
Gas (2%)

Warnings for Macrobid

Lung damage
Liver damage
Nerve damage (neuropathy)
Breakdown of red blood cells (hemolytic anemia)
Severe diarrhea

Summary for Keflex

Prescription only

Cephalexin, also commonly known as Keflex, is a cephalosporin antibiotic for people ages 1 year and older. It can treat many types of bacterial infections. This includes ear infections, skin infections like cellulitis, urinary tract infections (UTIs), and strep throat. Cephalexin comes as capsules, tablets, and a liquid suspension. It's taken by mouth 2 to 4 times per day. Side effects can include nausea, vomiting, and diarrhea. Cephalexin is a generic medication; its brand name Keflex is no longer available.

Indications for Keflex

Respiratory tract infections (e.g., strep throat)
Ear infections
Skin infections (e.g., cellulitis)
Bone infections
Urinary tract infections (UTIs)
Reproductive system infections (e.g., prostatitis)

Pros and Cons for Keflex

Pros

Treats several common types of bacterial infections
Okay for children as young as 1 year old to take
Available as a liquid for people who have trouble swallowing pills

Cons

Usually need to take a few times per day
Might not be able to take if you're allergic to penicillins or other cephalosporin antibiotics
Not recommended for the cold or flu (these are viral illnesses, not bacterial infections)