Comparative Pharmacology
Head-to-head clinical analysis: E MYCIN versus E E S 400.
Peer-Reviewed Evidence
Head-to-head clinical analysis: E MYCIN versus E E S 400.
E-MYCIN vs E.E.S. 400
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, a macrolide antibiotic, binds to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis. At high concentrations, it may also inhibit RNA synthesis.
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 infections caused by susceptible strains of microorganisms: respiratory tract infections (including Legionnaires disease, pertussis), skin and soft tissue infections, diphtheria, syphilis, chlamydial infections, and ocular infections in neonates.Prophylaxis of recurrent rheumatic fever.Off-label: gastrointestinal motility disorder (as a motilin agonist).
250-500 mg orally every 6 hours or 500 mg every 12 hours; maximum 4 g/day.
Erythromycin ethylsuccinate 400 mg orally every 6 hours. For severe infections, up to 4 g/day in divided doses.
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.
1.5-2.0 hours in adults with normal renal function; may be prolonged in hepatic impairment (up to 5-6 hours) but not significantly changed in renal disease.
Erythromycin is primarily metabolized by the liver via CYP3A4 isoenzyme. It undergoes demethylation and hydroxylation, producing active and inactive metabolites.
Primarily metabolized in the liver via demethylation by CYP3A4; undergoes N-demethylation and hydroxylation.
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 metabolites; approximately 2-5% renal excretion of unchanged drug; 5-15% fecal elimination.
65-90% bound primarily to albumin, with concentration-dependent binding; at therapeutic levels ~70-80% bound.
70-80% bound to albumin; binding is reversible and saturable at high concentrations.
0.5-1.2 L/kg, indicating extensive tissue distribution; concentrates in tissues (e.g., liver, spleen, tonsils) and intracellularly in phagocytes.
Approximately 0.7 L/kg (range 0.5-0.9 L/kg); indicates extensive tissue penetration including intracellular and inflammatory fluids.
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 (as erythromycin ethylsuccinate): approximately 30-65% (variable, reduced by food); intravenous: 100%.
No adjustment needed for mild to moderate renal impairment. For GFR <10 mL/min, use 50-60% of normal dose.
No specific dose adjustment required for renal impairment; caution with high doses in severe renal failure (CrCl <10 mL/min) due to potential ototoxicity.
Reduce dose by 50% in Child-Pugh class C cirrhosis; avoid in severe hepatic impairment.
In hepatic impairment, reduce dose by 50-75% depending on severity. Child-Pugh Class A: no adjustment; Class B: reduce to 50% of normal dose; Class C: avoid or use with extreme caution, maximum 1 g per day.
30-50 mg/kg/day orally divided every 6 hours; maximum 2 g/day.
30-50 mg/kg/day in 4 divided doses. For severe infections, up to 60-100 mg/kg/day. 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.
No specific dose adjustment; monitor for QT prolongation and hearing loss. Consider lower end of dosing range due to age-related decline in hepatic function.
E-MYCIN does not have a black box warning.
Increased risk of infantile hypertrophic pyloric stenosis (IHPS) when given to neonates. Erythromycin has also been associated with prolongation of the QT interval and risk of cardiac arrhythmias, including torsades de pointes.
["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"]
Hepatic dysfunction, QT prolongation (risk of arrhythmia), exacerbation of myasthenia gravis, Clostridioides difficile-associated diarrhea, ototoxicity (especially with high doses or renal impairment), potential for drug interactions (CYP3A4 inhibitors/inducers).
["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, concomitant use with terfenadine, astemizole, cisapride, pimozide, ergotamine, or dihydroergotamine (risk of cardiac arrhythmias).
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.
Take with food to minimize gastrointestinal upset. Avoid grapefruit juice as it can increase erythromycin concentrations via CYP3A4 inhibition. No other significant food interactions.
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.
FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; inadequate human studies in first trimester. No known risk of major birth defects or miscarriage. Avoid in maternal myasthenia gravis due to potential neonatal hypotonia.
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.
Compatible with breastfeeding. Erythromycin is excreted into breast milk in small amounts (M/P ratio approximately 0.5). No adverse effects reported in infants. Monitor infant for gastrointestinal disturbances or rash.
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 dose adjustment required. Physiologic changes in pregnancy (increased volume of distribution, renal clearance) do not necessitate dose changes for erythromycin. Standard adult dosing applies.
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).
E.E.S. 400 (erythromycin ethylsuccinate) is a macrolide antibiotic with bacteriostatic activity. It is a prodrug hydrolyzed to erythromycin base. Use with caution in patients with hepatic impairment or preexisting hearing loss. Monitor for QT prolongation, especially with concurrent use of other QT-prolonging drugs. Commonly used as an alternative in penicillin-allergic patients for respiratory tract infections. It also has prokinetic effects on the GI tract, which can be utilized in gastroparesis but may cause abdominal cramping.
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 this medication exactly as prescribed, usually every 6 hours or as directed.Complete the full course even if you feel better to prevent resistance.May cause stomach upset; taking with food can reduce GI irritation.Avoid grapefruit juice as it may affect drug levels.Report symptoms of liver problems (yellowing skin/eyes, dark urine) or hearing loss immediately.Do not take with certain medications like statins or warfarin without consulting your doctor.Use effective contraception if applicable, as erythromycin may reduce birth control pill efficacy.