Is erythromycin (macrolide antibiotic) safe for patients trying to conceive?

Erythromycin Safety for Patients Trying to Conceive

Erythromycin is safe to use in patients trying to conceive and during pregnancy, with the important exception that erythromycin estolate must be avoided due to maternal hepatotoxicity risk. 1, 2

Safety Profile During Conception and Pregnancy

FDA Classification and Evidence Base

• Erythromycin is classified as FDA Pregnancy Category B, indicating no evidence of fetal harm in animal studies at doses up to 3 times the maximum human dose 3
• The European Respiratory Society classifies erythromycin as "probably safe" during pregnancy (Category A/B), with most human studies finding no evidence of increased birth defects 1, 4
• Clinical use over 30+ years has established erythromycin as one of the safest antibiotics available 5

Specific Formulation Considerations

• Erythromycin base and erythromycin ethylsuccinate are safe options for use during conception and pregnancy 1, 2
• Erythromycin estolate is absolutely contraindicated during pregnancy due to drug-related hepatotoxicity 1, 2, 4

Clinical Effectiveness in Pregnancy

Treatment Success Rates

• Erythromycin achieves a 92% cure rate (98 of 107 patients) for chlamydial infections in pregnant women when used as erythromycin ethylsuccinate 400 mg four times daily for 7 days 6
• However, erythromycin has significantly lower efficacy (64-77%) compared to azithromycin for chlamydial infections and causes more gastrointestinal side effects 2

Recommended Dosing Regimens

When erythromycin is used during pregnancy for chlamydial infections, the CDC recommends these alternative regimens 1, 2:

• Erythromycin base 500 mg orally four times daily for 7 days, OR
• Erythromycin base 250 mg orally four times daily for 14 days (lower dose option if GI tolerance is a concern), OR
• Erythromycin ethylsuccinate 800 mg orally four times daily for 7 days, OR
• Erythromycin ethylsuccinate 400 mg orally four times daily for 14 days

Important Caveats and Pitfalls

Gastrointestinal Tolerability

• Gastrointestinal side effects (nausea, vomiting, abdominal pain, diarrhea) are common and dose-related, which may discourage patient compliance 1, 2
• Only 3% of patients (5 of 152) discontinued therapy due to GI intolerance in one pregnancy study, though this remains a clinical concern 6

Neonatal Considerations

• Very low risk of infantile hypertrophic pyloric stenosis (IHPS) exists in breastfed infants exposed during the first 13 days of life (not after 2 weeks) 1, 4
• One cohort study found 5% absolute risk of IHPS (7 of 157 exposed infants) when erythromycin was used in newborns 1, 4

Preferred Alternative

• Azithromycin 1 g orally as a single dose is now the preferred macrolide during pregnancy due to superior efficacy (94-100% cure rate), better tolerability, and excellent compliance 2, 7, 4
• Azithromycin is also FDA Pregnancy Category B with extensive safety data 7

When Erythromycin Should NOT Be Used

Absolute Contraindications

• History of hypersensitivity to any macrolide agent 1
• Concomitant use with astemizole, cisapride, pimozide, or terfenadine due to risk of fatal cardiac arrhythmias 1, 3
• Erythromycin estolate formulation during pregnancy 1, 2, 4

Clinical Situations Where Erythromycin Is Inadequate

• Syphilis treatment in pregnancy: erythromycin does not reliably cure fetal infection; penicillin with desensitization is required 4

Follow-Up Requirements

• Repeat testing 3 weeks after completion of therapy is mandatory for all pregnant women treated with erythromycin to ensure therapeutic cure 1, 2
• This is particularly important given erythromycin's lower efficacy compared to azithromycin and the potential sequelae for both mother and neonate if infection persists 2