Amoxicillin vs. Cephalexin

See how Amoxicillin and Cephalexin compare on approved uses, dosing, side effects, and cost.

Key Takeaways

  • Amoxicillin and cephalexin are both oral antibiotics used for many of the same respiratory, ear, and skin infections, but they come from different antibiotic classes with distinct allergy profiles.

  • Amoxicillin is a penicillin approved for a wider range of infections, including gonorrhea and H. pylori, while cephalexin is a cephalosporin often chosen for staph infections amoxicillin doesn't reliably cover.

  • Both are inexpensive generics, but cephalexin's price can climb higher at the top of its typical range than amoxicillin's.

Amoxicillin vs. Cephalexin Drug Summary

Amoxicillin

Amoxicillin is an aminopenicillin antibiotic used to treat ear, throat, respiratory, skin, and urinary infections, plus gonorrhea and H. pylori as part of combination therapy. It's taken orally as a capsule, tablet, chewable tablet, or liquid suspension, usually two to three times a day depending on the infection.

Cephalexin

Cephalexin is a first-generation cephalosporin antibiotic used to treat respiratory, ear, skin, bone, and urinary tract infections caused by susceptible bacteria. It's taken orally as a capsule, tablet, or liquid suspension, typically every 6 to 12 hours depending on the infection and dose.

Amoxicillin vs. Cephalexin Side Effects

Amoxicillin

Most common
Vomiting (greater than 1%)
Nausea (greater than 1%)
Diarrhea (greater than 1%)
Rash (greater than 1%)

Cephalexin

Most common
Vomiting (rate not specified in FDA label)
Nausea (rate not specified in FDA label)
Diarrhea (rate not specified in FDA label)
Dyspepsia (rate not specified in FDA label)

Amoxicillin vs. Cephalexin Dosage

Amoxicillin

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 250 mg every 8 hours At the start
Maximum dose 1 g three times daily If needed
Dose changes 4 increases As tolerated

Cephalexin

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 25-50 mg/kg/day divided At the start
Maximum dose 1 to 4 g/day divided If needed
Dose changes 4 increases As tolerated

Amoxicillin vs. Cephalexin Indications

Amoxicillin

Amoxicillin covers a broad range of common bacterial infections, from ear infections in children to urinary tract infections and uncomplicated gonorrhea in adults. It's also part of standard combination therapy for eradicating H. pylori, the bacteria linked to stomach ulcers.

  • Ear, nose, and throat infections

  • Lower respiratory tract infections

  • Skin and skin structure infections

  • Urinary tract infections

  • Gonorrhea and H. pylori (combination therapy)

Cephalexin

Cephalexin is FDA-approved for respiratory, ear, skin, bone, and genitourinary infections caused by susceptible strep and staph bacteria. It's often the choice when an infection specifically involves Staphylococcus aureus, since amoxicillin doesn't reliably cover it.

  • Respiratory infections (strep)

  • Otitis media (ear infections)

  • Skin and skin structure infections

  • Bone infections (staph, Proteus)

  • Genitourinary infections, including prostatitis

Amoxicillin vs. Cephalexin Pros and Cons

Amoxicillin

Amoxicillin has one of the longest safety track records of any antibiotic and is typically the first choice for common infections when no penicillin allergy exists. It's inexpensive and widely stocked, but it isn't effective against many staph infections and carries a well-known risk of rash in patients with mononucleosis.

Pros

  • Covers gonorrhea and H. pylori, unlike cephalexin

  • Decades of well-documented safety data since 1974

  • Available as a chewable tablet for easy pediatric dosing

Cons

  • Higher risk of rash in patients with mononucleosis

  • Doesn't reliably cover Staphylococcus aureus infections

  • Penicillin-class allergy risk, including rare anaphylaxis

Cephalexin

Cephalexin covers staphylococcal and some Proteus infections that amoxicillin can't reach, making it a go-to for certain skin, bone, and urinary infections. It requires dose adjustments in kidney impairment, and its FDA label doesn't specify exact side effect rates the way amoxicillin's does.

Pros

  • Covers Staphylococcus aureus and Proteus infections amoxicillin misses

  • FDA-approved for bone infections and acute prostatitis

  • Sometimes used off-label alongside acne treatment regimens

Cons

  • Requires dose adjustments for reduced kidney function

  • FDA label doesn't list specific side effect rates

  • Costs roughly $10 to $65 per 7-14 day course, which can run higher than amoxicillin's typical range

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