ERYC 125
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ERYC 125 (ERYC 125).
Erythromycin binds to the 50S subunit of bacterial ribosomes, inhibiting protein synthesis by blocking translocation of peptidyl-tRNA. It also activates motilin receptors in the gastrointestinal tract, enhancing gastric motility.
| Metabolism | Primarily hepatic via cytochrome P450 3A4 (CYP3A4) isoenzyme; undergoes demethylation and hydrolysis; major metabolite is desosamine. |
| Excretion | Primarily hepatic metabolism; ~2-5% excreted unchanged in urine, ~15-20% in bile/feces as active drug. |
| Half-life | 1.5-2.0 hours in adults; prolonged in hepatic impairment (up to 5-6 hours) or neonates. |
| Protein binding | 70-90% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.5-0.9 L/kg; indicates distribution into total body water with some tissue binding. |
| Bioavailability | Oral: ~35% (acid-labile, enteric-coated). |
| Onset of Action | Oral: 1-2 hours; topical: variable, within 1-2 hours for acne. |
| Duration of Action | 6-8 hours for typical dosing intervals; bacteriostatic for ~12 hours post-dose. |
250 mg orally every 6 hours or 500 mg every 12 hours; maximum 4 g/day.
| Dosage form | CAPSULE, DELAYED REL PELLETS |
| Renal impairment | No dose adjustment required for GFR >10 mL/min. For GFR <10 mL/min, reduce dose by 50% or extend interval to every 8-12 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment. Class B: reduce dose by 50%. Class C: reduce dose by 75% or avoid use. |
| Pediatric use | 30-50 mg/kg/day orally divided every 6-8 hours; maximum 2 g/day. |
| Geriatric use | No specific adjustment; monitor for ototoxicity and QT prolongation; consider lower initial dose due to age-related renal decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ERYC 125 (ERYC 125).
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.5. It is considered compatible with breastfeeding by the American Academy of Pediatrics, but may increase the risk of pyloric stenosis in neonates. Monitor for gastrointestinal symptoms in the infant. |
| Teratogenic Risk | Erythromycin, including ERYC 125, has not been associated with major congenital malformations in human studies. However, there is a potential increased risk of pyloric stenosis in infants exposed in utero or postnatally. No known teratogenic effects in first trimester; use in pregnancy is generally considered safe when indicated, especially for infections like chlamydia or syphilis. |
■ FDA Black Box Warning
No FDA boxed warning for ERYC 125.
| Serious Effects |
["Hypersensitivity to erythromycin or any macrolide antibiotic","Concomitant use with CYP3A4 substrates that prolong QT interval (e.g., terfenadine, astemizole, cisapride, pimozide)","Pre-existing QT prolongation or cardiac arrhythmia history"]
| Precautions | ["Risk of QT prolongation and ventricular arrhythmias (e.g., torsades de pointes), especially with other QT-prolonging drugs or electrolyte abnormalities","Hepatic impairment: monitor liver function","Potential for drug interactions via CYP3A4 inhibition","May exacerbate myasthenia gravis","Infantile hypertrophic pyloric stenosis (IHPS) risk in neonates"] |
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| Fetal Monitoring | Monitor maternal liver function tests during prolonged therapy due to potential hepatotoxicity. For fetal monitoring, assess for signs of pyloric stenosis in neonates if exposed near term. No routine fetal monitoring required for standard use. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies have not shown impaired fertility. However, erythromycin may rarely cause reversible infertility in males due to effects on sperm motility; this is uncommon. |