E.E.S.
Clinical safety rating: caution
Comprehensive clinical and safety monograph for E.E.S. (E.E.S.).
Erythromycin (E.E.S.) binds to the 50S subunit of bacterial ribosomes, inhibiting peptide chain elongation and protein synthesis. It also exhibits prokinetic effects on the gastrointestinal tract via motilin receptor agonism.
| Metabolism | Erythromycin is metabolized by cytochrome P450 3A4 (CYP3A4) enzymes; it also inhibits CYP3A4, leading to drug interactions. |
| Excretion | Primarily hepatic (biliary) excretion of unchanged drug and active metabolites; approximately 15% of an oral dose is excreted unchanged in urine. The remainder is eliminated via feces as unchanged drug and metabolites. |
| Half-life | 1.5-2 hours in adults with normal renal function; prolonged to 4-6 hours in patients with hepatic impairment; may be shorter in children. |
| Protein binding | 75-80% bound primarily to albumin; binding is saturable and decreased in hepatic impairment. |
| Volume of Distribution | 0.5-0.8 L/kg, indicating moderate tissue distribution; higher in infants (up to 1.2 L/kg). |
| Bioavailability | Oral: 35-40% due to incomplete absorption and first-pass metabolism; intramuscular: 75-85%; intravenous: 100%. |
| Onset of Action | Oral: 1-2 hours; intravenous: within minutes; intramuscular: 15-30 minutes. |
| Duration of Action | Approximately 6-12 hours; clinical effect persists for 8-12 hours after intravenous administration, though bacteriostatic activity may last longer. Reduced duration in hepatic impairment. |
250-500 mg every 6 hours orally or 15-20 mg/kg/day IV divided every 6 hours.
| Dosage form | TABLET, CHEWABLE |
| Renal impairment | No dose adjustment required; erythromycin undergoes minimal renal excretion. |
| Liver impairment | Use with caution; reduce dose in severe hepatic impairment (Child-Pugh C) by 50%. |
| Pediatric use | 30-50 mg/kg/day orally divided every 6 hours; maximum 2 g/day. |
| Geriatric use | Increased risk of QT prolongation and torsades de pointes; use lowest effective dose. Adjust for renal function if eGFR < 10 mL/min. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for E.E.S. (E.E.S.).
| Breastfeeding | Erythromycin is excreted into human milk in small amounts. The milk-to-plasma ratio (M/P) is approximately 0.5. Although generally considered compatible with breastfeeding, there is a potential for adverse effects such as gastrointestinal disturbances and alteration of infant gut flora. Caution advised, especially in neonates younger than 6 weeks, due to risk of hypertrophic pyloric stenosis. |
| Teratogenic Risk | Erythromycin ethylsuccinate (E.E.S.) is Pregnancy Category B. Animal studies have not demonstrated fetal risk, but no adequate controlled studies in pregnant women. Current evidence suggests no increased risk of major malformations. However, erythromycin base (oral) has been associated with a slightly increased risk of pyloric stenosis in infants exposed in utero, particularly in the first trimester. Use only if clearly needed. |
■ FDA Black Box Warning
Increased risk of QT interval prolongation and torsades de pointes, especially in patients with risk factors such as electrolyte abnormalities, bradycardia, or concurrent use of other QT-prolonging drugs. Fatal arrhythmias have been reported.
| Serious Effects |
["Hypersensitivity to erythromycin or any macrolide antibiotic","Patients with known QT interval prolongation or history of torsades de pointes","Concurrent use with CYP3A4 substrates that prolong QT interval (e.g., cisapride, pimozide, astemizole, terfenadine) due to risk of fatal arrhythmias","Hepatic impairment (relative contraindication, especially with estolate salt)","Infants <2 weeks of age with certain infections (relative contraindication due to IHPS risk)"]
| Precautions | ["QT prolongation and risk of cardiac arrhythmias (torsades de pointes); monitor electrolytes and avoid in patients with prolonged QT interval.","Hepatic toxicity (cholestatic jaundice) especially with estolate salt; monitor liver function.","Infantile hypertrophic pyloric stenosis (IHPS) reported in infants <6 weeks of age exposed to erythromycin; avoid use in this population unless essential.","Exacerbation of myasthenia gravis; use with caution in patients with neuromuscular disorders.","Clostridium difficile-associated diarrhea (CDAD); report any cases.","Ototoxicity (hearing loss) with high doses, especially in renal impairment.","Increased risk of cardiac death when used with drugs that inhibit CYP3A4 or prolong QT interval."] |
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| Fetal Monitoring | Monitor maternal liver function tests (LFTs) and renal function periodically. Assess for gastrointestinal side effects. For prolonged therapy, monitor for hearing loss (especially in renal impairment). Fetal monitoring: Standard prenatal care; no specific fetal monitoring required, but note potential infant pyloric stenosis risk. |
| Fertility Effects | No known adverse effects on fertility in animal studies. In humans, there is no evidence of fertility impairment from erythromycin. Macrolides have not been associated with decreased fertility in clinical use. |
| Food/Dietary | Avoid grapefruit juice (inhibits CYP3A4 metabolism, increases erythromycin levels). Take on empty stomach for optimal absorption; if GI upset, may take with small amount of food. Avoid concurrent ingestion of high-fat meals which may delay absorption. |
| Clinical Pearls | Erythromycin (E.E.S.) is a macrolide antibiotic that inhibits bacterial protein synthesis. It is a CYP3A4 inhibitor and can increase levels of statins, warfarin, and immunosuppressants. QT prolongation risk; avoid with other QTc-prolonging drugs. Administer on empty stomach for best absorption, but can be taken with food if GI upset occurs. Not effective against Haemophilus influenzae in children due to resistance. |
| Patient Advice | Take each dose with a full glass of water on an empty stomach (1 hour before or 2 hours after meals) unless stomach upset occurs, then may take with food. · Complete the full course even if you feel better to prevent resistance. · Avoid grapefruit juice during treatment as it may increase side effects. · Report immediately any signs of liver problems (yellowing skin/eyes, dark urine, persistent nausea) or irregular heartbeat. · Do not take with antacids containing aluminum or magnesium; separate by at least 2 hours. |