Comparative Pharmacology
Head-to-head clinical analysis: E MYCIN versus E E S.
Peer-Reviewed Evidence
Head-to-head clinical analysis: E MYCIN versus E E S.
E-MYCIN vs E.E.S.
Head-to-head clinical comparison of therapeutic indices and safety profiles.
Erythromycin binds to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis by blocking the translocation of peptidyl-tRNA. It may also act as a motilin receptor agonist, enhancing gastrointestinal motility.
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.
Treatment of upper respiratory tract infections (e.g., streptococcal pharyngitis, tonsillitis)Lower respiratory tract infections (e.g., pneumonia, bronchitis) caused by susceptible organismsSkin and soft tissue infectionsPertussis (whooping cough)Diphtheria (adjunctive therapy)Chlamydial infections (e.g., urethritis, cervicitis, trachoma)Legionnaires' diseaseSyphilis (alternative to penicillin)Intestinal amebiasisPrevention of rheumatic fever recurrenceProkinetic agent for gastroparesis (off-label)
Treatment of acute otitis mediaTreatment of pharyngitis/tonsillitis due to Streptococcus pyogenesTreatment of pneumonia due to Mycoplasma pneumoniae, Legionella pneumophila, and Chlamydia trachomatisTreatment of pertussisTreatment of uncomplicated skin and skin structure infectionsTreatment of acne vulgaris (topical or systemic low-dose)Treatment of diphtheriaTreatment of syphilis (primary and secondary)Treatment of chlamydial infections during pregnancyTreatment of nongonococcal urethritisProphylaxis of recurrent rheumatic feverOff-label: improvement of gastric motility in gastroparesis
250-500 mg orally every 6 hours or 500 mg every 12 hours; maximum 4 g/day.
250-500 mg every 6 hours orally or 15-20 mg/kg/day IV divided every 6 hours.
None Documented
None Documented
1.5-2 hours in adults with normal renal function; prolonged to 4-6 hours in severe hepatic impairment; no significant change in renal impairment due to minimal renal clearance.
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.
Erythromycin is primarily metabolized by the liver via CYP3A4 isoenzyme. It undergoes demethylation and hydroxylation, producing active and inactive metabolites.
Erythromycin is metabolized by cytochrome P450 3A4 (CYP3A4) enzymes; it also inhibits CYP3A4, leading to drug interactions.
Primarily hepatic metabolism and biliary excretion with significant enterohepatic circulation; approximately 2-15% excreted unchanged in urine; 10-40% excreted in feces via bile; less than 1% eliminated as unchanged drug in feces from unabsorbed drug.
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.
65-90% bound primarily to albumin, with concentration-dependent binding; at therapeutic levels ~70-80% bound.
75-80% bound primarily to albumin; binding is saturable and decreased in hepatic impairment.
0.5-1.2 L/kg, indicating extensive tissue distribution; concentrates in tissues (e.g., liver, spleen, tonsils) and intracellularly in phagocytes.
0.5-0.8 L/kg, indicating moderate tissue distribution; higher in infants (up to 1.2 L/kg).
Oral base: ~30-40% (acid-labile; enteric-coated preparations improve); estolate: ~100% (due to enhanced absorption and decreased first-pass); stearate and ethylsuccinate: ~40-60% (fasting reduces absorption of stearate; ethylsuccinate absorption is food-dependent).
Oral: 35-40% due to incomplete absorption and first-pass metabolism; intramuscular: 75-85%; intravenous: 100%.
No adjustment needed for mild to moderate renal impairment. For GFR <10 mL/min, use 50-60% of normal dose.
No dose adjustment required; erythromycin undergoes minimal renal excretion.
Reduce dose by 50% in Child-Pugh class C cirrhosis; avoid in severe hepatic impairment.
Use with caution; reduce dose in severe hepatic impairment (Child-Pugh C) by 50%.
30-50 mg/kg/day orally divided every 6 hours; maximum 2 g/day.
30-50 mg/kg/day orally divided every 6 hours; maximum 2 g/day.
Use lower end of dose range (250-500 mg every 6 hours) due to increased risk of QT prolongation and drug interactions.
Increased risk of QT prolongation and torsades de pointes; use lowest effective dose. Adjust for renal function if eGFR < 10 mL/min.
E-MYCIN does not have a 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.
["Hepatic dysfunction: may cause cholestatic hepatitis, especially with estolate salt","Prolongation of QT interval and risk of torsades de pointes, especially with other QT-prolonging drugs or electrolyte abnormalities","Infantile hypertrophic pyloric stenosis (IHPS) in neonates exposed to erythromycin","Clostridioides difficile-associated diarrhea (CDAD)","Exacerbation of myasthenia gravis","Ototoxicity (reversible, mainly with high doses or renal impairment)","Antagonism with clindamycin and chloramphenicol"]
["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."]
["Hypersensitivity to erythromycin or any macrolide antibiotic","Concomitant use with ergotamine or dihydroergotamine (ergotism risk)","Concomitant use with cisapride, pimozide, astemizole, terfenadine, or other QT-prolonging agents (risk of torsades de pointes)","History of cholestatic jaundice or hepatic impairment associated with prior erythromycin use"]
["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)"]
Data Pending Review
Data Pending Review
Grapefruit juice may increase erythromycin levels due to CYP3A4 inhibition. High-fat meals may decrease absorption. Concurrent ingestion of alcohol is not recommended as it may increase hepatotoxicity risk.
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.
E-MYCIN (erythromycin base) is generally considered low risk in pregnancy. Data from large cohort studies and meta-analyses do not show an increased risk of major congenital malformations after first trimester exposure. However, erythromycin estolate has been associated with an increased risk of maternal hepatotoxicity; preparations other than estolate are preferred. During second and third trimesters, erythromycin has been used for the treatment of genital mycoplasma infections and for Group B Streptococcus prophylaxis. There is a possible increase in pyloric stenosis risk in infants exposed in utero, particularly when used late in pregnancy, but absolute risk remains low. Use only if clearly needed.
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.
Erythromycin is excreted into human breast milk in small amounts. The average milk-to-plasma ratio is approximately 0.5. Levels are usually low, but can accumulate with high maternal doses. No adverse effects have been reported in breastfed infants, though there is a theoretical risk of alteration in infant gut flora or drug resistance. The American Academy of Pediatrics considers erythromycin compatible with breastfeeding. Caution with prolonged or high-dose therapy due to risk of infant gastrointestinal effects.
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.
No specific dose adjustments are required for erythromycin base or stearate during pregnancy. The pharmacokinetics of erythromycin are not significantly altered by pregnancy. Dosing should be based on the indication and patient weight, using standard doses. Avoid erythromycin estolate due to increased risk of maternal hepatotoxicity. For Group B Streptococcus prophylaxis, use standard intrapartum dosing (500 mg IV every 6 hours).
No specific dose adjustment required for erythromycin ethylsuccinate in pregnancy solely due to pregnancy. Pharmacokinetic changes in pregnancy (increased volume of distribution, enhanced clearance) may reduce serum levels, but typical dosing regimens (e.g., 400 mg q6h for adults) remain effective. Monitor clinical response. For severe infections, consider serum level monitoring if available.
Category C
Category C
E-MYCIN (erythromycin) is a macrolide antibiotic with bacteriostatic activity against Gram-positive cocci and atypical pathogens. Notable for QT prolongation risk, especially with other QT-prolonging drugs. Also a motilin agonist, used off-label for gastroparesis at lower doses. Administer with food to reduce GI upset. Avoid in hepatic impairment or concurrent statin use (increases statin myopathy risk).
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.
Take this medication with a full glass of water, with or without food.Complete the full course even if you feel better.Avoid grapefruit juice as it can affect drug levels.Report any signs of liver problems (yellowing eyes/skin, dark urine, abdominal pain).Inform your doctor if you have heart rhythm problems or take other medications.
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.