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Compare Flagyl vs. Keflex

Head-to-head comparisons of medication uses, side effects, warnings, and more.

Key takeaways

Metronidazole (Flagyl) and cephalexin are both antibiotics, but they belong to different classes and treat different types of infections. Metronidazole is a nitroimidazole antibiotic that treats bacterial and parasitic infections, such as trichomoniasis and bacterial vaginosis. It is taken three times a day and should not be mixed with alcohol due to serious side effects. Cephalexin, on the other hand, is a cephalosporin antibiotic used to treat bacterial infections like UTIs, ear infections, and respiratory infections. It is typically taken 2 to 4 times a day and does not have a direct interaction with alcohol. Metronidazole can cause a metallic taste and in rare cases serious brain and nerve problems, while cephalexin can lead to allergic reactions and C. difficile-related diarrhea. Both medications are available as lower-cost generics and require a prescription.

  • Metronidazole (Flagyl)
    Cephalexin
  • Metronidazole (Flagyl)
    Cephalexin

  • Summary of Flagyl vs. Keflex

    Summary for Nitroimidazole antibiotic
    Prescription only

    Metronidazole (Flagyl) is an oral antibiotic for adults and children. It's used to treat certain bacterial and parasitic infections, including bacterial vaginosis (a type of vaginal bacteria infection) and trichomoniasis (a sexually transmitted infection, or STI). Metronidazole (Flagyl) is taken by mouth, typically 3 times a day. Some common side effects of this medication include diarrhea, nausea, and vomiting. Avoid drinking alcohol while taking and for 3 days after stopping metronidazole (Flagyl) because this combination can cause a serious reaction. Metronidazole (Flagyl) is available as a lower-cost generic.

    Summary for Cephalosporin antibiotic
    Prescription only

    Cephalexin is a common antibiotic that's used to treat many different bacterial infections including urinary tract infections (UTIs), ear infections, and sinus infections, to name a few. Cephalexin is a cephalosporin antibiotic that kills bacteria to fight the infection. It's safe to use in people over the age of 1, and it's typically taken by mouth 2 to 4 times per day. This medication is available as a lower-cost generic capsule, tablet, and suspension; the brand name Keflex is no longer available. Side effects can include nausea, vomiting, and diarrhea.

  • Indications of Flagyl vs. Keflex

    Indications for

    Treatment of certain bacterial and parasitic infections, including:

    •Trichomoniasis
    •Amebiasis (parasitic gut infection)
    •Serious bacterial infections, such as:
    •Abdominal infection (including peritonitis)
    •Skin infections
    •Gynecological infections (including endometritis)
    •Bloodstream infection (septicemia)
    •Bone and joint infections
    •Central nervous system infections (meningitis)
    •Lung infections (lower respiratory tract infections)
    •Heart infection (endocarditis)
    Indications for
    •Respiratory tract infections
    •Ear infections
    •Skin infections
    •Bone infections
    •Urinary tract infections (UTIs)
    •Reproductive system infections

  • Pros and Cons of Flagyl vs. Keflex

    Pros and Const for Nitroimidazole antibiotic
    Pros
    •Taken by mouth
    •Available as a lower-cost generic medication
    •Can be used to treat different types of bacterial infection
    •Immediate-release formulations can be taken with or without food
    Cons
    •Immediate-release formulations needs to be taken multiple times a day for most infections
    •Serious interaction with alcohol
    •Can cause metallic taste in mouth
    •Not recommended while breastfeeding
    Pros and Const for Cephalosporin antibiotic
    Pros
    •Treats several common types of bacterial infections
    •Can use for adults and children over the age of 1
    •Available as a liquid for people who have trouble swallowing pills
    •Available as a lower-cost generic
    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)

  • Common Side Effects of Flagyl vs. Keflex

    Common Side Effects for

    Please note: These are common side effects reported by people who took extended-release metronidazole (Flagyl)

    •Headache (18%)
    •Inflammation of the vagina (15%)
    •Nausea (10%)
    •Metallic taste (9%)
    •Flu-like symptoms (6%)
    Common Side Effects for
    •Diarrhea
    •Nausea
    •Vomiting
    •Indigestion
    •Stomach pain

  • Warnings of Flagyl vs. Keflex

    Common Side Effects for
    •Possible risk of cancer
    •Serious allergic reactions
    •Brain and nerve problems
    •Liver and kidney problems
    •Risk of fungal infection
    •Risk of drug resistance
    •Lower white blood cell counts
    •Interaction with other medications
    Common Side Effects for
    •Allergic reactions
    •Diarrhea from Clostridioides difficile infection
    •Development of drug-resistant bacteria
    •Seizures
    •Higher risk of bleeding

  • Prices with our coupons for Flagyl vs. Keflex

    Learn more about Metronidazole
    Learn more about Cephalexin

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