Overview
Erythromycin ethylsuccinate is a macrolide antibiotic used to treat various bacterial infections. It works by inhibiting bacterial protein synthesis and is commonly prescribed for respiratory tract infections, skin infections, and certain sexually transmitted diseases. The medication is available in oral suspension form and requires careful consideration of drug interactions due to its CYP3A4 inhibition properties.
Mechanism of Action
Erythromycin ethylsuccinate inhibits bacterial protein synthesis by reversibly binding to the 50S ribosomal subunit of susceptible bacteria, preventing translocation of aminoacyl transfer-RNA and inhibiting peptide chain elongation.
Indications
- Upper respiratory tract infections caused by Streptococcus pyogenes, Streptococcus pneumoniae, or Haemophilus influenzae (with sulfonamides)
- Lower respiratory tract infections caused by Streptococcus pneumoniae or Streptococcus pyogenes
- Skin and skin structure infections caused by Streptococcus pyogenes or Staphylococcus aureus
- Pertussis (whooping cough) caused by Bordetella pertussis
- Mycoplasma pneumoniae respiratory infections
- Chlamydia trachomatis infections including conjunctivitis, pneumonia, and urogenital infections
- Syphilis in penicillin-allergic patients
- Intestinal amebiasis caused by Entamoeba histolytica
- Legionnaires' Disease caused by Legionella pneumophila
- Prophylaxis of rheumatic fever in penicillin-allergic patients
Common Doses
- 400 mg
- 200 mg/5mL suspension
- Dosing based on 30-50 mg/kg/day for pediatric patients
Dosage
Dosage varies by age, weight, and infection severity. For mild to moderate infections in children: 30-50 mg/kg/day divided every 6 hours. For adults: 400 mg every 6 hours, up to 4 g daily for severe infections. Streptococcal infections require at least 10 days of therapy. Can be administered without regard to meals.
Contraindications
- Known hypersensitivity to erythromycin
- Concomitant use with terfenadine, astemizole, pimozide, or cisapride
- Concomitant use with HMG-CoA reductase inhibitors extensively metabolized by CYP3A4 (lovastatin, simvastatin)
Side Effects
- Gastrointestinal: nausea, vomiting, abdominal pain, diarrhea, anorexia
- Hepatic dysfunction and abnormal liver function tests
- QT prolongation and ventricular arrhythmias
- Allergic reactions including urticaria and anaphylaxis
- Skin reactions from mild eruptions to Stevens-Johnson syndrome
- Pseudomembranous colitis
- Interstitial nephritis
- Pancreatitis
- Reversible hearing loss (especially in renal impairment)
Interactions
- Theophylline: increased serum levels and potential toxicity
- Digoxin: elevated serum levels
- Oral anticoagulants: increased anticoagulant effects
- CYP3A4 substrates: elevated concentrations of multiple drugs including benzodiazepines, statins, sildenafil, cyclosporine, carbamazepine
- Ergot alkaloids: acute ergot toxicity contraindicated
- Calcium channel blockers: hypotension and bradyarrhythmias
- Colchicine: potentially life-threatening toxicity
Counseling Points
- Complete full course of therapy even if symptoms improve
- May be taken with or without food
- Report severe diarrhea, abdominal pain, or blood/mucus in stool
- Inform healthcare provider of all medications including over-the-counter drugs
- Report any signs of allergic reaction or unusual heart rhythms
- Use additional contraception if taking oral contraceptives due to potential decreased efficacy
- Avoid grapefruit juice which may increase drug levels