What symptoms does erythromycin treat?

October 12, 2025 •

4 min read

First introduced for clinical use over 70 years ago, erythromycin is a macrolide antibiotic that remains a valuable treatment option for various bacterial infections. To understand what symptoms does erythromycin treat, it is crucial to recognize that its effectiveness is limited to infections caused by specific susceptible bacteria.

Quick Summary

Erythromycin is a macrolide antibiotic used to treat numerous bacterial infections, including respiratory, skin, eye, and sexually transmitted diseases. It works by inhibiting bacterial protein synthesis.

Key Points

Treats Respiratory Infections: Erythromycin is prescribed for infections like pneumonia, bronchitis, and whooping cough, addressing symptoms such as severe coughing and difficulty breathing.
Effective for Skin Conditions: Topical and oral erythromycin treat acne, cellulitis, and impetigo by controlling bacterial growth and resolving painful lesions.
Manages STIs: Symptoms of chlamydia, and historically syphilis and gonorrhea, can be managed with erythromycin, offering an alternative for those with penicillin allergies.
Resolves Eye Infections: The ophthalmic ointment form treats bacterial conjunctivitis (pink eye) and is used to prevent eye infections in newborns.
Addresses Gastrointestinal Issues: It is used for intestinal amebiasis and some bacterial diarrhea caused by Campylobacter.
Inhibits Bacterial Growth: As a bacteriostatic macrolide, erythromycin works by inhibiting bacterial protein synthesis, preventing the bacteria from multiplying.
Causes Gastrointestinal Side Effects: Common side effects include nausea, vomiting, and diarrhea, which are often more frequent than with newer macrolides.

Understanding Erythromycin

Erythromycin is an antibiotic from the macrolide class, derived from the soil-dwelling bacterium Saccharopolyspora erythraea. As a broad-spectrum, bacteriostatic agent, its primary action is to stop the growth of bacteria rather than killing them outright. It accomplishes this by binding to the 50S ribosomal subunit of susceptible microorganisms, which inhibits protein synthesis and halts the bacteria's ability to multiply. Because humans possess different ribosomal subunits (40S and 60S), erythromycin does not interfere with protein production in human cells. This makes it a targeted and effective treatment for specific bacterial illnesses.

Respiratory Tract Infections

Erythromycin is a well-established treatment for various respiratory infections and is often a choice for patients with a penicillin allergy.

Pneumonia: Including community-acquired pneumonia and Legionnaires' disease caused by Legionella pneumophila.
Bronchitis: Particularly acute exacerbations caused by Streptococcus pneumoniae or Haemophilus influenzae.
Whooping Cough (Pertussis): Caused by Bordetella pertussis, erythromycin can eliminate the causative organism from the nasopharynx, reducing contagiousness, especially when administered early.
Diphtheria: As an adjunct to antitoxin, it can help eradicate the Corynebacterium diphtheriae organism and prevent a carrier state.
Other infections: Also effective against infections caused by Mycoplasma pneumoniae and Chlamydia pneumoniae.

Skin and Soft Tissue Infections

Topical and oral formulations of erythromycin are used to combat various skin conditions by targeting surface bacteria.

Acne vulgaris: Topical erythromycin is a common treatment for acne, working by controlling the bacteria Propionibacterium that contribute to breakouts. It can also be combined with other topical agents like benzoyl peroxide.
Impetigo: A common, contagious skin infection that presents as red sores on the face.
Cellulitis and erysipelas: These bacterial skin infections are often caused by Streptococcus pyogenes.
Rosacea: Erythromycin can be used to treat the inflammatory papules associated with rosacea.

Sexually Transmitted Infections (STIs)

Erythromycin serves as an alternative treatment for several STIs, particularly for patients with a penicillin hypersensitivity.

Chlamydia: Used to treat urogenital infections and conjunctivitis in newborns caused by Chlamydia trachomatis.
Syphilis: While penicillin is the drug of choice, erythromycin has historically been used for primary syphilis in penicillin-allergic patients. However, the CDC no longer recommends it for syphilis due to reported treatment failures.
Gonorrhea: Can be used as an alternative for certain types of gonorrhea infections in penicillin-intolerant patients.
Other STIs: Also used for chancroid and granuloma inguinale.

Eye and Gastrointestinal Infections

Erythromycin's utility extends to infections beyond the respiratory tract and skin.

Bacterial Conjunctivitis: The ophthalmic ointment form is used to treat bacterial eye infections, including pink eye.
Neonatal Eye Infections: Administered at birth to prevent eye infections in newborns caused by gonorrhea and chlamydia.
Intestinal Amebiasis: Effective in treating intestinal infections caused by Entamoeba histolytica.
Campylobacter enteritis: Treats this form of bacterial diarrhea.

Comparing Erythromycin to Newer Macrolides

Since the introduction of erythromycin, newer macrolide antibiotics like azithromycin and clarithromycin have been developed, offering improved properties. These comparisons are vital for healthcare providers when choosing the most appropriate treatment.


Feature	Erythromycin	Clarithromycin	Azithromycin
Dosing Frequency	2 to 4 times a day	2 times a day	Once a day, or shorter courses
Gastrointestinal (GI) Side Effects	Higher incidence due to motilin agonism	Moderate incidence	Lower incidence
Spectrum of Activity	Effective against many gram-positive and some gram-negative bacteria	Broad spectrum, improved against H. influenzae	Broad spectrum, improved against H. influenzae and C. trachomatis
Half-Life	Shorter half-life (1.5-2 hours)	Longer half-life	Significantly longer half-life
Drug Interactions	Significant CYP3A4 inhibitor, high potential for interactions	CYP3A4 inhibitor, moderate potential for interactions	Fewer drug interactions, does not significantly inhibit CYP3A4
Cost	Generally less expensive	Moderate cost	Higher cost, though potentially more cost-effective due to better compliance

Potential Side Effects and Precautions

Like all medications, erythromycin can cause side effects. The most common are gastrointestinal, including nausea, vomiting, diarrhea, and abdominal cramps. To minimize GI upset, taking the medication with food can be helpful.

More serious, though rare, side effects can occur. These include liver problems (manifesting as jaundice or dark urine), serious skin reactions (like Stevens-Johnson syndrome), and an irregular heartbeat (QT prolongation), which can be fatal in rare cases. Due to the risk of QT prolongation, erythromycin should be used with caution in patients with pre-existing heart conditions or those taking other QT-prolonging drugs.

Conclusion

Erythromycin is a versatile macrolide antibiotic that effectively treats the symptoms of numerous bacterial infections affecting the respiratory system, skin, eyes, and genitourinary tract. Its ability to inhibit bacterial growth by disrupting protein synthesis makes it a potent weapon against pathogens like Streptococcus, Legionella, and Chlamydia. While newer macrolides offer advantages in terms of dosing convenience, fewer side effects, and expanded spectrum, erythromycin remains a significant treatment option, particularly as an alternative for penicillin-allergic patients. Understanding the specific conditions it treats and potential side effects is vital for safe and effective use. As antibiotic resistance continues to be a global concern, using antibiotics appropriately, including completing the full prescribed course, is essential for preserving their efficacy for future use. MedlinePlus provides more detailed drug information on erythromycin.

Frequently Asked Questions

No, erythromycin is a macrolide antibiotic and is not effective against viral infections such as the common cold or flu. It only works by inhibiting the growth of susceptible bacteria.

Erythromycin works by binding to the 50S ribosomal subunit of bacteria, which blocks protein synthesis. This action prevents the bacteria from growing and multiplying, thereby resolving the infection.

Yes, erythromycin is often used as an alternative for patients with penicillin allergies, particularly for infections caused by Streptococcus, such as strep throat, and for treating certain STIs.

The most common side effects are gastrointestinal, including nausea, vomiting, diarrhea, and stomach pain. Taking the medication with food can help alleviate these symptoms.

While it was historically used for primary syphilis in penicillin-allergic patients, the CDC no longer recommends erythromycin due to reports of treatment failures. Other treatments are now preferred.

Newer macrolides like azithromycin and clarithromycin generally offer improved oral bioavailability, less frequent dosing, and better tolerability (fewer GI side effects) compared to erythromycin.

If you miss a dose, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and continue your regular schedule. Do not take a double dose to catch up.