Amoxicillin vs. Zithromax

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

Key Takeaways

  • Amoxicillin is a low-cost penicillin antibiotic taken two to three times daily for 5 to 14 days, while Zithromax is a macrolide often finished in just 5 days or even a single dose.

  • Zithromax carries FDA warnings for QT prolongation and liver toxicity that amoxicillin's label does not include.

  • Amoxicillin causes rash more often, especially in people with mononucleosis, while Zithromax's most common side effect is nausea.

Amoxicillin vs. Zithromax Drug Summary

Amoxicillin

Amoxicillin is an aminopenicillin, a subtype of penicillin antibiotic, used to treat ear, sinus, throat, skin, and urinary tract infections, along with gonorrhea and H. pylori as part of combination therapy. It comes as capsules, tablets, chewable tablets, or a liquid suspension and is usually taken two to three times a day for 5 to 14 days.

Zithromax

Zithromax (azithromycin) is a macrolide antibiotic used for respiratory, skin, and certain sexually transmitted infections, as well as prevention of MAC disease in people with weakened immune systems. It comes as tablets or a liquid suspension and is often taken as a short 5-day course or a single dose, since it stays active in tissue long after the last dose.

Amoxicillin vs. Zithromax Side Effects

Amoxicillin

Most common
vomiting (greater than 1%)
nausea (greater than 1%)
diarrhea (greater than 1%)
rash (greater than 1%)

Zithromax

Most common
vomiting (2% to 7%)
nausea (3% to 18%)
diarrhea (5% to 14%)
abdominal pain (3% to 7%)

Amoxicillin vs. Zithromax Dosage

Amoxicillin

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 1 g three times daily At the start
Maximum dose 1 g three times daily Same as starting
Dose changes None Fixed dose

Zithromax

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 500 mg once daily Day 1
Maximum dose 12 mg/kg once daily Days 1-5
Dose changes 2 increases As tolerated

Amoxicillin vs. Zithromax Indications

Amoxicillin

Amoxicillin treats common bacterial infections of the ear, nose, throat, lungs, skin, and urinary tract, and is also used for uncomplicated gonorrhea and as part of combination therapy for H. pylori. It is not effective against viral infections and can trigger a widespread rash if given to someone with mononucleosis.

  • Ear, nose, and throat infections

  • Lower respiratory tract infections

  • Skin and skin structure infections

  • Urinary tract infections

  • H. pylori eradication (combination therapy)

Zithromax

Zithromax treats respiratory infections like pneumonia, bronchitis flare-ups, and sinusitis, along with skin infections and certain sexually transmitted infections such as chlamydia. It is also used to prevent and treat MAC disease in people with weakened immune systems, and is sometimes prescribed off-label for traveler's diarrhea.

  • Community-acquired pneumonia

  • Acute bacterial sinusitis

  • Skin and skin structure infections

  • Chlamydia and gonorrhea infections

  • MAC disease prevention and treatment

Amoxicillin vs. Zithromax Pros and Cons

Amoxicillin

Amoxicillin has been used safely for decades and remains one of the most affordable antibiotics available, with dosing forms suited to both adults and children. It does not carry the cardiac or liver warnings seen with some other antibiotic classes, but it typically requires more frequent dosing over a longer course.

Pros

  • Roughly $11 to $25 per month, among the cheapest antibiotics

  • Long track record of safety since 1974

  • Available in chewable tablets for children

  • No FDA cardiac (QT prolongation) warning

Cons

  • Usually dosed two to three times a day

  • Higher risk of rash, especially with mononucleosis

  • Not active against atypical bacteria like Chlamydia

  • Courses often run 7 to 14 days

Zithromax

Zithromax's long tissue half-life allows short courses or single-dose treatment, which can improve how reliably patients finish therapy. It covers some atypical bacteria amoxicillin does not reach, but its label carries added warnings around heart rhythm and liver safety.

Pros

  • Short 5-day or single-dose regimens for many infections

  • Covers atypical bacteria such as Chlamydia and Mycoplasma

  • Also approved for MAC disease prevention and treatment

  • Stays active in tissue for days after the last dose

Cons

  • Roughly $45 to $150 per course, pricier than amoxicillin

  • FDA warning for QT prolongation and arrhythmia risk

  • Risk of serious, sometimes fatal, liver toxicity

  • Higher rates of nausea and diarrhea in trials

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