What are the uses of erythromycin?

Erythromycin Uses

Erythromycin is FDA-approved for treating respiratory tract infections (upper and lower), skin and soft tissue infections, pertussis, chlamydial infections (including neonatal conjunctivitis and urogenital infections), Legionnaires' disease, and as an alternative for primary syphilis in penicillin-allergic patients. 1

FDA-Approved Indications

Respiratory Tract Infections

• Upper respiratory infections caused by Streptococcus pyogenes, Streptococcus pneumoniae, and Haemophilus influenzae (when combined with sulfonamides, as many H. influenzae strains resist erythromycin alone) 1
• Lower respiratory infections of mild to moderate severity from S. pyogenes or S. pneumoniae 1
• Mycoplasma pneumoniae respiratory infections 1
• Legionnaires' disease caused by Legionella pneumophila 1

Skin and Soft Tissue Infections

• Mild to moderate skin infections from Streptococcus pyogenes or Staphylococcus aureus (note: resistant staphylococci may emerge during treatment) 1
• Erythrasma caused by Corynebacterium minutissimum 1

Chlamydial Infections

• Neonatal conjunctivitis caused by Chlamydia trachomatis 1
• Pneumonia of infancy from C. trachomatis 1
• Urogenital infections during pregnancy from C. trachomatis 1
• Uncomplicated urethral, endocervical, or rectal infections in adults when tetracyclines are contraindicated or not tolerated 1

Other Bacterial Infections

• Pertussis (whooping cough) caused by Bordetella pertussis - eliminates organism from nasopharynx and may provide prophylaxis in exposed individuals 1
• Diphtheria from Corynebacterium diphtheriae as adjunct to antitoxin 1
• Listeriosis caused by Listeria monocytogenes 1
• Intestinal amebiasis from Entamoeba histolytica (oral forms only; extraenteric disease requires other agents) 1
• Nongonococcal urethritis from Ureaplasma urealyticum when tetracyclines contraindicated 1
• Primary syphilis from Treponema pallidum as alternative in penicillin-allergic patients (requires spinal fluid examination before and after treatment) 1

Pelvic Inflammatory Disease

• Acute PID from Neisseria gonorrhoeae in penicillin-allergic women (IV erythromycin lactobionate followed by oral erythromycin base; requires syphilis testing before treatment and 3 months after) 1

Prophylaxis

• Prevention of rheumatic fever as alternative when penicillin cannot be used for S. pyogenes pharyngitis 1
• Preoperative prophylaxis for elective colon operations 2

CDC Guideline-Based Dosing for Key Indications

Chlamydial Infections in Adults

• Alternative regimen: Erythromycin base 500 mg orally four times daily for 7 days OR erythromycin ethylsuccinate 800 mg orally four times daily for 7 days 3
• Important caveat: Erythromycin is less efficacious than azithromycin or doxycycline, and gastrointestinal side effects frequently reduce compliance 3

Chlamydial Infections in Pregnancy

• Recommended regimen: Erythromycin base 500 mg orally four times daily for 7 days 3
• Alternative regimens: Erythromycin base 250 mg four times daily for 14 days, OR erythromycin ethylsuccinate 800 mg four times daily for 7 days, OR erythromycin ethylsuccinate 400 mg four times daily for 14 days 3
• Critical warning: Erythromycin estolate is contraindicated in pregnancy due to hepatotoxicity risk 3, 4
• Follow-up: Repeat testing (preferably culture) 3 weeks after completion recommended due to lower efficacy 3

Chlamydial Infections in Children

• Children <45 kg: Erythromycin 50 mg/kg/day divided into four doses for 10-14 days 3
• Children >1 month: 40-50 mg/kg/day divided into four doses for 14 days (maximum 2 g/day) 4
• Important note: Treatment effectiveness is approximately 80%; second course may be required 3
• Neonates <1 month: Azithromycin preferred over erythromycin due to infantile hypertrophic pyloric stenosis (IHPS) risk 4

Nongonococcal Urethritis

• Alternative regimen: Erythromycin base 500 mg orally four times daily for 7 days OR erythromycin ethylsuccinate 800 mg orally four times daily for 7 days 3
• For recurrent/persistent urethritis: Metronidazole 2 g orally single dose PLUS erythromycin base 500 mg four times daily for 7 days OR erythromycin ethylsuccinate 800 mg four times daily for 7 days 3

Pertussis

• Adult dosing: 2 g daily divided into 4 doses for 14 days 4
• Completing full 14-day course is essential to prevent relapses 4

Common Pitfalls and Caveats

Gastrointestinal Tolerability

• Frequent GI side effects (nausea, vomiting, abdominal pain, diarrhea) often discourage compliance, making erythromycin less desirable than azithromycin or doxycycline for chlamydial infections 3, 4
• High doses increase adverse effect risk 4

Drug Interactions

• Do not use concurrently with astemizole, cisapride, pimozide, or terfenadine 4
• Unlike azithromycin, erythromycin has significant drug interactions with theophylline, terfenadine, and carbamazepine 5

Pregnancy Considerations

• Avoid erythromycin estolate in pregnancy due to hepatotoxicity 3, 4
• Erythromycin base and ethylsuccinate are acceptable alternatives 3

Neonatal Safety

• Increased IHPS risk in neonates during month following administration; azithromycin preferred in infants <1 month 4

Resistance Patterns

• Many H. influenzae strains are not susceptible to erythromycin concentrations ordinarily achieved; must combine with sulfonamides 1
• Resistant staphylococci may emerge during treatment of skin infections 1

Clinical Efficacy Considerations

• For chlamydial infections, azithromycin (single 1 g dose) or doxycycline (100 mg twice daily for 7 days) are preferred over erythromycin due to superior efficacy and tolerability 3
• Test of cure may be considered 3 weeks after erythromycin completion (not needed for azithromycin/doxycycline) 3