Azithromycin Vs. Erythromycin: Drug Comparison

Azithromycin is the active ingredient in the brand-name medication Zithromax^®. The information below is about brand name Zithromax. According to the FDA, “Generic medicines use the same active ingredients as brand-name medicines and work the same way, so they have the same risks and benefits as the brand-name medicines.”

Zithromax (azithromycin) is an antibiotic used to treat bacterial infections by inhibiting bacterial protein synthesis, preventing the growth and spread of bacteria. Its FDA-approved indications include the treatment of respiratory infections, skin infections, sexually transmitted infections, and certain ear infections. Off-label uses may include treating conditions like traveler’s diarrhea or certain tick-borne infections. Zithromax is available in tablet, liquid suspension, and intravenous forms. Common side effects include nausea, diarrhea, and abdominal pain. Caution is advised due to the risk of QT prolongation, a heart rhythm disorder, especially in patients with existing heart conditions or those taking other medications that affect heart rhythm.

Erythromycin is an antibiotic that works by inhibiting bacterial protein synthesis, preventing bacteria from growing and reproducing. It is FDA-approved for the treatment of a variety of bacterial infections, including respiratory tract infections, skin infections, and sexually transmitted infections like chlamydia. Erythromycin is available in oral tablets, topical forms, and intravenous solutions. Common side effects include gastrointestinal upset, nausea, and abdominal pain, and it can interact with other medications that affect liver enzymes, potentially causing serious heart rhythm disturbances. It should be used cautiously with other drugs that prolong the QT interval.

Macrolide antibacterial

Macrolide antibiotic

Zithromax (azithromycin) is indicated for mild to moderate infections caused by designated, susceptible bacteria:

• Sexually transmitted diseases

• Mycobacterial infections

To reduce the development of drug-resistant bacteria and maintain the effectiveness of erythromycin and other antibacterial drugs, erythromycin should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria

• Typically taken orally once daily

• Comes in 600 mg tablets and 1,000 mg/5 mL oral suspension

• Typically taken orally four times daily

• Comes in 250 mg and 500 mg tablets

The most common adverse reactions are:

• Diarrhea (5%)

• Nausea (3%)

• Abdominal pain (3%)

• Vomiting

The most frequent side effects of oral erythromycin preparations are gastrointestinal and are dose related. They include:

• Nausea

• Vomiting

• Abdominal pain

• Diarrhea

• Anorexia

• Patients with known hypersensitivity to azithromycin, erythromycin, any macrolide, or ketolide antibiotic

• Patients with a history of cholestatic jaundice/hepatic dysfunction associated with prior use of azithromycin

• Drug interactions: nelfinavir, warfarin

• Erythromycin is contraindicated in patients with known hypersensitivity to this antibiotic

• Erythromycin is contraindicated in patients taking terfenadine, astemizole, cisapride, pimozide, ergotamine, or dihydroergotamine

• Do not use erythromycin concomitantly with HMG CoA reductase inhibitors (statins) that are extensively metabolized by CYP 3A4 (lovastatin or simvastatin), due to the increased risk of myopathy, including rhabdomyolysis

• Drug interactions: theophylline, verapamil, digoxin, anticoagulants, drugs metabolized by CYP3A, ergotamine/dihydroergotamine, triazolobenzodiazepines, statins, sildenafil, colchicine, and others

• Serious (including fatal) allergic and skin reactions

• Liver toxicity

• Infantile hypertrophic pyloric stenosis (IHPS)

• Prolongation of QT interval and cases of torsades de pointes have been reported

• Cardiovascular death

• Clostridioides difficile-associated diarrhea

• Zithromax may exacerbate muscle weakness in persons with myasthenia gravis

• Liver toxicity

• QT prolongation

• Syphilis in pregnancy

• Clostridium difficile-associated diarrhea (CDAD)

• Breastfeeding: Caution should be exercised when erythromycin is administered to a nursing woman

*This information is from the label for brand name Zithromax^®. See the Full Prescribing Information for more complete information. Azithromycin, the active ingredient in Zithromax, may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient azithromycin.

*This information is from the erythromycin label used by Alembic Pharmaceuticals Inc. See the Full Prescribing Information for more complete information. Erythromycin may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient erythromycin.