Erythromycin Usage & Dosage Guide

Available Formulations

Erythromycin is available in multiple formulations to accommodate different clinical needs, patient populations, and routes of administration. Each formulation has unique pharmacokinetic properties affecting absorption, bioavailability, and dosing schedules.

Oral Formulations

Parenteral Formulation

• Erythromycin Lactobionate: 500mg, 1g powder for IV infusion (reconstitute with sterile water)

Topical Formulations

• Erythromycin 2% gel: 30g, 60g tubes for acne vulgaris
• Erythromycin 2% solution: 60mL bottles with applicator pads
• Erythromycin 2% ointment: 25g tubes for skin infections
• Combination products: Erythromycin 3% + benzoyl peroxide 5% gel

Ophthalmic Formulation

• Erythromycin 0.5% ophthalmic ointment: 3.5g tubes for conjunctivitis and neonatal prophylaxis

Adult Dosing Guidelines

Standard Oral Dosing

Note: Ethylsuccinate produces lower serum levels; doses are approximately 1.6× those of base/stearate.

Intravenous Dosing

• Standard dose: 15–20mg/kg/day divided q6h (maximum 4g/day)
• Severe infections: Up to 4g/day in divided doses
• Gastroparesis: 200–250mg IV q6–8h (infused over 45–60 minutes)

IV Administration:

• Reconstitute with sterile water (1g in 20mL)
• Further dilute in 100–250mL normal saline or D5W
• Infuse over 20–60 minutes (rapid infusion increases risk of arrhythmias)
• Maximum concentration: 5mg/mL for peripheral administration

Topical Dosing

• Acne vulgaris: Apply 2% gel/solution twice daily to affected areas
• Skin infections: Apply 2% ointment 2–3 times daily
• Duration: 6–12 weeks for acne; 7–10 days for infections

Ophthalmic Dosing

• Conjunctivitis: Apply 0.5–1cm ribbon to affected eye(s) 2–8 times daily
• Prophylaxis (neonates): Single 0.5–1cm ribbon to each eye within 1 hour of birth

Pediatric Dosing

Age-Based Oral Dosing

Specific Pediatric Indications

• Pertussis: 40–50mg/kg/day (base) divided q6h × 14 days
• Pertussis prophylaxis: 40–50mg/kg/day divided q6h × 10 days
• Chlamydial conjunctivitis/pneumonia: 50mg/kg/day (base) divided q6h × 14 days
• Streptococcal pharyngitis: 40mg/kg/day divided q6–8h × 10 days

Administration Guidelines

Food Interactions by Formulation

Important Administration Notes

• Do not crush or chew enteric-coated tablets
• Shake suspensions well before measuring dose
• Use calibrated measuring device for liquid formulations
• Store reconstituted suspension at room temperature; discard after 10 days
• Separate from antacids by at least 2 hours
• Complete full course even if symptoms improve

Dose Adjustments

Renal Impairment

No adjustment needed for mild-moderate impairment (CrCl >10 mL/min). In severe impairment or dialysis:

• Consider 50–75% of normal dose
• Maximum 1.5g/day in severe renal failure
• Not removed by hemodialysis or peritoneal dialysis

Hepatic Impairment

• Use with caution; erythromycin is hepatically metabolized
• Avoid estolate formulation (increased hepatotoxicity risk)
• Monitor liver function tests
• Consider dose reduction in severe cirrhosis

Elderly Patients

• No routine dose adjustment needed
• Increased risk of ototoxicity with high doses
• Monitor for QT prolongation
• Consider drug interactions with concurrent medications

Special Populations

Pregnancy

• FDA Category B (except estolate: contraindicated)
• Preferred macrolide in pregnancy
• Treatment of choice for chlamydial infections in pregnancy
• Use standard adult doses

Lactation

• Excreted in breast milk (small amounts)
• Generally considered compatible with breastfeeding
• Monitor infant for diarrhea, thrush
• Alternative feeding method if infant develops adverse effects

Obesity

• Use actual body weight for dosing
• Maximum doses still apply
• Consider IV route for severe infections (better tissue penetration)

Therapeutic Monitoring

Clinical Response

• Improvement typically seen within 48–72 hours
• Complete course even if symptoms resolve
• Consider alternative therapy if no improvement by day 3

Laboratory Monitoring

• Baseline liver function tests for prolonged therapy
• Monitor INR if on warfarin (significant interaction)
• Consider ECG if risk factors for QT prolongation
• Culture and sensitivity for treatment failures

Missed Doses

Patient counseling for missed doses:

• Take missed dose as soon as remembered
• Skip if almost time for next dose
• Do not double doses
• Maintain regular dosing schedule
• Set reminders for multiple daily doses

Storage Requirements

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