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. |
| Molecular Weight | 733.93 |
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 | Erythromycin (as estolate) has been associated with an increased risk of cardiovascular malformations in some studies; use only if clearly needed. There is no evidence of teratogenicity for erythromycin base or stearate. |
| 2nd trimester | Generally considered safe; no known association with fetal harm. May be used if indicated. |
| 3rd trimester | Safe for use; no known adverse fetal effects near term. |
Clinical note
Comprehensive clinical and safety monograph for ERYC 125 (ERYC 125).
| Placental transfer | Erythromycin crosses the placenta; fetal serum levels are approximately 5-20% of maternal serum levels. |
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts (less than 2% of maternal dose). It is generally considered compatible with breastfeeding. However, there is a theoretical risk of alteration of infant gut flora and sensitization. The estolate salt may increase risk of infantile hypertrophic pyloric stenosis, especially in infants under 2 weeks old; therefore, estolate salts should be avoided during breastfeeding if alternatives exist. |
■ FDA Black Box Warning
No FDA boxed warning for ERYC 125.
| Serious Effects |
Known hypersensitivity to erythromycin or any macrolide antibioticConcurrent use with cisapride, pimozide, terfenadine, astemizole, ergotamine, or dihydroergotamine due to risk of QT prolongation and cardiac arrhythmiasPre-existing QT interval prolongation or cardiac arrhythmias (e.g., torsades de pointes)Electrolyte disturbances (hypokalemia, hypomagnesemia)
| 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 |
| Food/Dietary | Grapefruit and grapefruit juice should be avoided as they can increase drug levels and risk of toxicity. Food does not significantly alter absorption of the ethylsuccinate formulation, but taking with a high-fat meal may slightly delay absorption. Avoid alcohol as it may increase risk of hepatotoxicity. |
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| Lactation Rating | L2 - Probably Compatible (for base/stearate); L3 - Possibly Unsafe (for estolate due to pyloric stenosis risk) |
| 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. |
| 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. |
| Clinical Pearls | ERYC 125 (erythromycin ethylsuccinate) is a macrolide antibiotic; note that it may prolong QT interval, especially when combined with other QT-prolonging drugs. Avoid use in patients with hepatic impairment or known cholestatic jaundice. Administer on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption, but food does not significantly affect the ethylsuccinate formulation. |
| Patient Advice | Take exactly as prescribed; do not skip doses or stop early even if you feel better. · Take this medication on an empty stomach, at least 1 hour before or 2 hours after a meal. · Avoid grapefruit and grapefruit juice while taking this medicine. · Report any signs of liver problems: yellowing of skin/eyes, dark urine, severe stomach pain. · Notify your doctor immediately if you experience irregular heartbeat, fainting, or severe diarrhea. · Complete the full course to prevent antibiotic resistance. |