Azithromycin vs. Cephalexin

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

Key Takeaways

  • Azithromycin is a macrolide antibiotic typically taken for 3 to 5 days, while cephalexin is a first-generation cephalosporin usually taken for 7 to 14 days with multiple daily doses.

  • Azithromycin carries FDA warnings for QT interval prolongation and liver toxicity that cephalexin does not share.

  • Cephalexin is often chosen for skin, bone, and urinary infections, while azithromycin is more commonly used for respiratory infections and certain sexually transmitted infections.

Azithromycin vs. Cephalexin Drug Summary

Azithromycin

Azithromycin is a macrolide antibiotic used to treat respiratory infections, skin infections, and certain sexually transmitted infections. It is usually taken as a short 3 to 5 day oral course, though single-dose regimens exist for some conditions. Its long tissue half-life allows for fewer doses than many other antibiotics.

Cephalexin

Cephalexin is a first-generation cephalosporin antibiotic used to treat respiratory, skin, bone, and urinary tract infections. It is taken orally, usually every 6 to 12 hours for 7 to 14 days depending on the infection. It has been used safely since the early 1970s and remains a common first-choice antibiotic for many outpatient infections.

Azithromycin vs. Cephalexin Side Effects

Azithromycin

Most common
Nausea (up to 18%)
Vomiting (up to 7%)
Abdominal pain (up to 7%)
Diarrhea (up to 14%)

Cephalexin

Most common
Nausea (up to 1%)
Vomiting (up to 1%)
Abdominal pain (up to 1%)
Dyspepsia (up to 1%)

Azithromycin vs. Cephalexin Dosage

Azithromycin

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 500 mg once Day 1
Maximum dose 5 mg/kg once daily Days 2-5
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 25-50 mg/kg/day divided Same as starting
Dose changes None Fixed dose

Azithromycin vs. Cephalexin Indications

Azithromycin

Azithromycin is FDA-approved to treat a range of bacterial infections including pneumonia, bronchitis, sinusitis, pharyngitis, skin infections, and certain sexually transmitted infections like chlamydia and chancroid. It is also used off-label for traveler's diarrhea and as prophylaxis in select populations exposed to chlamydia. It is not effective against viral infections such as colds or flu.

  • Community-acquired pneumonia

  • Acute bacterial sinusitis and bronchitis

  • Pharyngitis and tonsillitis

  • Urethritis, cervicitis, and chancroid

  • Pelvic inflammatory disease and otitis media

Cephalexin

Cephalexin is FDA-approved to treat respiratory tract infections, otitis media, skin and skin structure infections, bone infections, and genitourinary infections including prostatitis. It is also used off-label as an adjunct for acne and for surgical site infection prevention. It is not effective against viral infections such as colds, flu, or COVID-19.

  • Respiratory tract infections

  • Otitis media

  • Skin and skin structure infections

  • Bone infections

  • Genitourinary infections including prostatitis

Azithromycin vs. Cephalexin Pros and Cons

Azithromycin

Azithromycin's long tissue half-life allows for very short treatment courses, sometimes just a single dose, which can improve adherence. It also covers atypical respiratory pathogens and several sexually transmitted infections that cephalexin does not treat. It carries FDA warnings for QT prolongation and liver toxicity that require caution in certain patients.

Pros

  • Short 3 to 5 day or single-dose regimens

  • Covers atypical respiratory pathogens

  • Effective against chlamydia and chancroid

  • Convenient once-daily dosing

Cons

  • Risk of QT prolongation and heart rhythm effects

  • Rare but serious liver toxicity warning

  • More drug interactions via macrolide metabolism

  • Not indicated for bone infections

Cephalexin

Cephalexin has a long history of safe use since the early 1970s and does not carry a QT prolongation warning. It works well for skin, bone, and urinary infections but requires more frequent dosing over a longer 7 to 14 day course. Patients with penicillin allergy may have some risk of cross-reactivity with this cephalosporin.

Pros

  • No QT prolongation warning

  • Long track record of safety since the 1970s

  • Effective for bone and urinary infections

  • Fewer major drug interactions

Cons

  • Requires dosing multiple times daily

  • Longer 7 to 14 day treatment course

  • Possible cross-reactivity in penicillin allergy

  • Not effective against atypical respiratory pathogens

Common Symptoms and Related Diseases You Can Explore

Explore a range of common symptoms the Doctronic Symptom Checker can help you understand.