What is the usual dose of erythromycin?

Erythromycin Usual Dosing

The usual dose of erythromycin is 40 mg/kg/day divided into 4 doses (maximum 2 g/day) for children, or 250 mg four times daily (or 500 mg twice daily) for adults. 1

Pediatric Dosing

For children, the standard dose is 30-50 mg/kg/day divided into equally spaced doses, typically given every 6 hours (four times daily). 1 This dosing applies to most common indications including respiratory tract infections and skin infections. 2

• For more severe infections, this dosage may be doubled but should not exceed 4 g per day. 1
• For atypical pneumonia (Mycoplasma, Chlamydia), the recommended dose is 40 mg/kg/day in 4 divided doses. 2
• For pertussis treatment or prophylaxis, use 40-50 mg/kg/day in 4 divided doses (maximum 2 g/day) for 14 days. 3, 1

Intravenous Dosing in Children

When IV erythromycin lactobionate is required, administer 20 mg/kg/day divided every 6 hours. 2 The infusion should be given slowly over ≥60 minutes to reduce gastrointestinal adverse effects. 4, 5

Adult Dosing

The usual adult dose is 250 mg four times daily or 500 mg every 12 hours. 1 Dosage may be increased up to 4 g per day according to infection severity, though twice-daily dosing is not recommended when doses larger than 1 g daily are administered. 1

• For pneumonia in adolescents, the British Thoracic Society recommends 500 mg four times daily for 7-10 days (may extend to 14 days based on clinical response). 3
• For Chlamydia trachomatis infections, use 500 mg four times daily for at least 7 days. 1

Important Administration Considerations

Optimal blood levels are obtained when erythromycin is given in the fasting state—at least 30 minutes and preferably 2 hours before meals. 1 However, in most patients, erythromycin tablets may be dosed without regard to meals. 1

Minimizing Gastrointestinal Side Effects

Erythromycin causes significantly more gastrointestinal side effects compared to other macrolides like azithromycin. 3 To improve tolerance:

• Limit daily doses to less than 4 g. 6
• Take medication with milk or food if GI symptoms occur. 6
• Use enteric-coated formulations when available. 3
• For IV administration, infuse over 60 minutes rather than 30 minutes to reduce nausea and vomiting by 79%. 5

Critical Safety Warnings

Erythromycin should be avoided in neonates under 1 month due to risk of hypertrophic pyloric stenosis. 4 In this age group, azithromycin is the preferred macrolide. 4

Do not administer erythromycin with astemizole, cisapride, pimozide, or terfenadine due to risk of severe cardiac arrhythmias. 3 Erythromycin can cause potentially fatal episodes of ventricular tachycardia associated with QTc interval prolongation, especially in neonates. 4

When to Choose Alternative Macrolides

Azithromycin is preferred over erythromycin for most respiratory infections due to better tolerability, fewer gastrointestinal side effects, and more convenient once-daily dosing. 4, 3 Consider azithromycin (10 mg/kg day 1, then 5 mg/kg days 2-5) or clarithromycin (15 mg/kg/day in 2 doses) as alternatives with superior tolerability profiles. 2, 3

Common Prescribing Errors to Avoid

• Do not prescribe courses shorter than 14 days for pertussis or other serious infections, as relapse rates increase. 3
• Do not use erythromycin as first-line for typical bacterial pneumonia caused by S. pneumoniae or H. influenzae; beta-lactams (amoxicillin) remain preferred. 3
• Do not combine with aluminum- or magnesium-containing antacids, as they reduce absorption. 4
• Monitor carefully when combining with drugs metabolized by cytochrome P450 enzymes due to high potential for drug interactions. 2, 3