What are the indications, dosage, and contraindications for erythromycin capsules?

INDICATION OF CAP ERYTHROMYCIN AND DOSAGE AND CONTRAINDICATION

Erythromycin capsules are indicated for bacterial infections including pertussis, respiratory tract infections (upper and lower), skin infections, chlamydial infections, and as an alternative for penicillin-allergic patients, with standard adult dosing of 250 mg four times daily or 500 mg twice daily for 10-14 days depending on the infection. 1

Indications

Erythromycin capsules are FDA-approved for treatment of:

Respiratory Infections:

• Upper respiratory tract infections caused by Streptococcus pyogenes, Streptococcus pneumoniae, and Haemophilus influenzae (when combined with sulfonamides)
• Lower respiratory tract infections from S. pyogenes or S. pneumoniae
• Pertussis (whooping cough) caused by Bordetella pertussis - effective for eliminating organism and prophylaxis in exposed individuals
• Mycoplasma pneumoniae respiratory infections
• Legionnaires' Disease caused by Legionella pneumophila 1

Skin and Soft Tissue:

• Mild to moderate skin infections from S. pyogenes or Staphylococcus aureus (though resistant staphylococci may emerge) 1

Chlamydial Infections:

• Conjunctivitis of the newborn
• Pneumonia of infancy
• Urogenital infections during pregnancy
• Uncomplicated urethral, endocervical, or rectal infections when tetracyclines contraindicated 1

Other Indications:

• Intestinal amebiasis (Entamoeba histolytica)
• Acute pelvic inflammatory disease (Neisseria gonorrhoeae) as alternative
• Primary syphilis (Treponema pallidum) in penicillin-allergic patients
• Diphtheria and erythrasma
• Rheumatic fever prophylaxis in penicillin-allergic patients 1

Dosage

Adults:

• Standard dose: 250 mg four times daily OR 500 mg every 12 hours 1
• Severe infections: Up to 4 g per day in divided doses
• Pertussis: 2 g per day in 4 divided doses for 14 days 2
• Chlamydial urogenital infections: 500 mg four times daily for at least 7 days 1
• Primary syphilis: 30-40 g total given in divided doses over 10-15 days 1
• Legionnaires' Disease: 1-4 g daily in divided doses 1

Children:

• Standard dose: 30-50 mg/kg/day in equally divided doses (maximum 4 g/day) 1
• Severe infections: May double dose but not exceed 4 g/day
• Pertussis: 40-50 mg/kg/day in 4 divided doses for 14 days (maximum 2 g/day) 2
• Chlamydial conjunctivitis/pneumonia: 50 mg/kg/day in 4 divided doses for at least 2-3 weeks 1

Critical Pediatric Caveat - Infants <1 Month: Erythromycin is NOT preferred in neonates due to risk of infantile hypertrophic pyloric stenosis (IHPS). Azithromycin is the recommended macrolide for this age group. If azithromycin is unavailable and erythromycin must be used, dose is 40-50 mg/kg/day in 4 divided doses with mandatory monitoring for IHPS 2. The risk-benefit calculation changes only when treating life-threatening pertussis where disease mortality outweighs IHPS risk.

Administration: Best absorbed on empty stomach (at least 30 minutes, preferably 2 hours before meals), though may be taken with food if GI upset occurs 1

Duration:

• Streptococcal infections: minimum 10 days
• Pertussis: 14 days (due to relapse risk with shorter courses) 2
• Most other infections: 7-14 days depending on severity

Contraindications

Absolute Contraindications:

• Known hypersensitivity to erythromycin or any macrolide antibiotic 2, 1
• Concomitant use with: terfenadine, astemizole, cisapride, pimozide, ergotamine, or dihydroergotamine - risk of serious cardiovascular events including QT prolongation, cardiac arrest, torsades de pointes, and ventricular arrhythmias 2, 1

Relative Contraindications/Cautions:

• Infants <1 month old - high risk of IHPS; use only if azithromycin unavailable 2
• Hepatic impairment - monitor closely
• Concurrent use with CYP3A substrates requires careful monitoring due to drug interactions 2

Critical Drug Interactions

Erythromycin inhibits cytochrome P450 (CYP3A), causing elevated concentrations of drugs metabolized by this pathway. Monitor closely or avoid concurrent use with:

• Alfentanil, bromocriptine, cyclosporine, carbamazepine, cilostazol, disopyramide
• Ergot alkaloids, statins (lovastatin/simvastatin), methylprednisolone, quinidine
• Benzodiazepines (triazolam, alprazolam), sildenafil, tacrolimus, vinblastine
• Theophylline, digoxin, oral anticoagulants, phenytoin, valproate 2

Common Adverse Effects

Most frequent (dose-related):

• Gastrointestinal: epigastric distress, abdominal cramps, nausea, vomiting, diarrhea (more frequent and severe than other macrolides) 2
• Hypersensitivity reactions: skin rashes, drug fever, eosinophilia
• Rare but serious: cholestatic hepatitis, sensorineural hearing loss, anaphylaxis 2

Special Population Considerations:

• Pregnancy Category B - no adequate human studies but animal studies show no fetal risk 2
• Breastfeeding: Use with caution; one case report of pyloric stenosis in breastfed infant whose mother took erythromycin 2