What is Erythromycin Best Used For?

October 7, 2025 •

4 min read

First discovered in 1952, erythromycin is a macrolide antibiotic with a long history of use against various bacterial infections. This medication remains a valuable treatment option, especially for patients with a penicillin allergy, and understanding what is erythromycin best used for is key to its effective application.

Quick Summary

Erythromycin is a macrolide antibiotic used to treat numerous bacterial infections, including respiratory, skin, eye, and sexually transmitted diseases, and is a viable alternative for penicillin-allergic patients.

Key Points

Macrolide Antibiotic: Erythromycin is a macrolide antibiotic that works by inhibiting bacterial protein synthesis, making it effective against a range of gram-positive and some gram-negative bacteria.
Respiratory and Skin Infections: It is primarily used to treat respiratory infections like pneumonia, Legionnaires' disease, and whooping cough, as well as skin conditions such as acne and erythrasma.
Penicillin Alternative: Erythromycin is a valuable alternative for patients who are allergic to penicillin, enabling treatment for conditions like strep throat, syphilis, and rheumatic fever prophylaxis.
Variety of Formulations: The medication is available in different forms, including oral tablets and suspensions, topical treatments for skin, and ophthalmic ointment for eye infections, including prevention in newborns.
Promotility Agent for Gastroparesis: Beyond its antibiotic properties, erythromycin acts as a motilin receptor agonist to increase gut motility and can be used off-label for short-term treatment of gastroparesis.
Considerable Drug Interactions: Patients should be aware of significant drug interactions, including with statins and certain heart medications, and should avoid grapefruit while on the drug.

What is Erythromycin?

Erythromycin is an antibiotic that belongs to the macrolide class of drugs, which work by stopping the growth of certain bacteria. It achieves this by binding to the 50S subunit of the bacteria's ribosome, effectively inhibiting protein synthesis and preventing the bacteria from multiplying. This action makes it a bacteriostatic antibiotic, meaning it prevents bacterial growth rather than directly killing the bacteria. Because humans have different ribosomal subunits, erythromycin does not affect protein synthesis in human cells, making it a targeted therapy.

Primary Uses of Erythromycin

Erythromycin has a broad spectrum of activity against many types of bacteria, making it effective for treating a wide array of infections in various parts of the body.

Respiratory Tract Infections

Pneumonia: Erythromycin is often used to treat specific types of pneumonia caused by bacteria such as Streptococcus pneumoniae and Mycoplasma pneumoniae.
Legionnaires' Disease: It is an established treatment for this severe type of lung infection, which is caused by the bacterium Legionella pneumophila.
Pertussis (Whooping Cough): Erythromycin is used to treat and prevent whooping cough by eliminating the causative organism, Bordetella pertussis, from the nasopharynx.
Diphtheria: The drug is used as an adjunct to antitoxin treatment to help eliminate the Corynebacterium diphtheriae bacteria.

Skin and Soft Tissue Infections

Acne: Topical erythromycin is commonly prescribed, sometimes in combination with other agents like benzoyl peroxide, to control and treat acne vulgaris. Oral forms may also be used.
Rosacea: Due to its anti-inflammatory properties, topical and oral erythromycin can help manage skin inflammation associated with rosacea.
Erythrasma: This chronic bacterial skin infection, caused by Corynebacterium minutissimum, is effectively treated with erythromycin.
Other Infections: Mild to moderate skin infections like impetigo or boils, typically caused by Streptococcus pyogenes or Staphylococcus aureus, can also be treated.

Sexually Transmitted and Gynecological Infections

Chlamydia: Erythromycin is an alternative treatment for urogenital infections caused by Chlamydia trachomatis, particularly for pregnant women and neonates.
Syphilis: For individuals with a penicillin allergy, erythromycin serves as an alternative therapy for primary syphilis.
Pelvic Inflammatory Disease (PID): It may be used in certain cases of PID, often as an alternative for penicillin-allergic patients.

Ophthalmic and Newborn Uses

Neonatal Conjunctivitis: Ophthalmic erythromycin ointment is routinely administered to newborns to prevent eye infections from bacteria, including those acquired during birth.
Bacterial Eye Infections: The ophthalmic ointment is used to treat specific bacterial eye infections like bacterial conjunctivitis and blepharitis in adults and children.

Special and Prophylactic Applications

Beyond its primary use for active infections, erythromycin is also utilized in specific clinical contexts:

Gastroparesis: Erythromycin is a motilin receptor agonist, meaning it stimulates contractions of the smooth muscle in the gut. This pro-motility effect can be used for short-term treatment of diabetic gastroparesis to help improve gastric emptying.
Rheumatic Fever Prophylaxis: It is used to prevent recurrent attacks of rheumatic fever in patients who have a history of the condition and are allergic to penicillin.

Comparison of Oral and Topical Erythromycin


Feature	Oral Erythromycin	Topical Erythromycin
Primary Uses	Respiratory tract infections, STIs, intestinal infections, severe skin infections.	Mild to moderate acne, rosacea, erythrasma.
Administration	Taken by mouth as a tablet, capsule, or liquid suspension.	Applied directly to the skin as a solution, gel, or ointment.
Onset of Action	Typically works within a few days for most infections.	Can take several weeks to months to see significant improvement for skin conditions.
Potential Side Effects	Nausea, vomiting, diarrhea, stomach cramps; rarer but serious effects like heart rhythm problems.	Skin irritation, dryness, or stinging at the application site.
Key Considerations	Potential for significant drug interactions; avoid grapefruit.	Less risk of systemic side effects and drug interactions.

Potential Side Effects and Drug Interactions

Erythromycin can cause side effects ranging from mild to severe. Common side effects often include gastrointestinal issues such as stomach upset, diarrhea, and nausea. Serious but less common side effects can include allergic reactions (hives, rash, difficulty breathing), liver problems, and irregular heartbeats.

It is important to discuss all medications with a healthcare provider, as erythromycin can interact with other drugs. Key interactions include those with cholesterol-lowering statins, some antiarrhythmic medications, and blood thinners like warfarin, which can increase the risk of adverse effects. Additionally, consuming grapefruit or grapefruit juice can raise erythromycin levels in the body, increasing the risk of side effects, and should be avoided.

Conclusion

In summary, erythromycin is best used for a specific set of bacterial infections, particularly respiratory and skin conditions, as well as several sexually transmitted infections. Its role as an alternative for penicillin-allergic patients and its use in treating gastroparesis highlight its versatility. While newer macrolides like azithromycin are often preferred due to better tolerance and more convenient dosing, erythromycin remains an important therapeutic option in clinical practice. As with any antibiotic, it should be taken exactly as prescribed to ensure effectiveness and minimize the risk of bacterial resistance. To learn more about its specific uses and safety information, consult the MedlinePlus drug information page on erythromycin.

Frequently Asked Questions

For most bacterial infections, you can expect to start feeling better within a few days of starting erythromycin. However, for skin conditions like acne and rosacea, it may take several weeks to see a noticeable improvement.

No, erythromycin is a macrolide antibiotic and is only effective against infections caused by bacteria. It is not an effective treatment for viral illnesses like the common cold or the flu.

Yes, erythromycin is from a different class of antibiotics (macrolides) and is often prescribed as an alternative for patients who are allergic to penicillin.

Yes, it is important to avoid eating grapefruit or drinking grapefruit juice while taking erythromycin, as it can increase the amount of the medication in your body and raise the risk of side effects.

Yes, in rare cases, erythromycin can cause heart rhythm problems, including a condition called prolonged QT interval. This is more likely to occur in individuals with pre-existing heart conditions.

Erythromycin eye ointment can be used to treat bacterial pink eye (conjunctivitis). However, it is important to note that it will not be effective if the pink eye is caused by a virus or other non-bacterial pathogen.

Erythromycin can be used off-label as a short-term treatment for gastroparesis. It acts on motilin receptors in the gut, which increases stomach muscle motility and helps improve gastric emptying.