Comparative Pharmacology
Head-to-head clinical analysis: E MYCIN versus E E S 200.
Peer-Reviewed Evidence
Head-to-head clinical analysis: E MYCIN versus E E S 200.
E-MYCIN vs E.E.S. 200
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 acts by binding to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis by blocking translocation of peptidyl-tRNA. It may also inhibit ribosomal assembly.
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, pertussis, diphtheria, chlamydial infections, syphilis, Legionnaires' diseaseProphylaxis of recurrent rheumatic feverOff-label: gastroparesis, as a prokinetic agent
250-500 mg orally every 6 hours or 500 mg every 12 hours; maximum 4 g/day.
400 mg orally every 6 hours as the ethylsuccinate salt. Maximum daily dose 4 g.
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.
Approximately 1.5-2 hours in adults with normal renal function; may be prolonged to 5-6 hours in severe renal impairment.
Erythromycin is primarily metabolized by the liver via CYP3A4 isoenzyme. It undergoes demethylation and hydroxylation, producing active and inactive metabolites.
Metabolized primarily via hepatic CYP3A4 and is a moderate inhibitor of CYP3A4. Eliminated mainly in bile, with some renal excretion.
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 metabolism and biliary excretion; approximately 5-15% of active drug excreted renally, with fecal elimination accounting for the majority of the remaining dose.
65-90% bound primarily to albumin, with concentration-dependent binding; at therapeutic levels ~70-80% bound.
70-80% bound primarily to alpha-1-acid glycoprotein (AAG) and to a lesser extent albumin.
0.5-1.2 L/kg, indicating extensive tissue distribution; concentrates in tissues (e.g., liver, spleen, tonsils) and intracellularly in phagocytes.
0.5-0.9 L/kg; extensive tissue penetration (except CSF and brain unless meninges inflamed).
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: 25-50% (base); variable due to acid instability; enteric-coated formulations improve absorption.
No adjustment needed for mild to moderate renal impairment. For GFR <10 mL/min, use 50-60% of normal dose.
No dose adjustment required for GFR >10 mL/min. For GFR <10 mL/min, reduce dose by 25-50% or administer at prolonged intervals.
Reduce dose by 50% in Child-Pugh class C cirrhosis; avoid in severe hepatic impairment.
Child-Pugh A: No adjustment. Child-Pugh B: Reduce dose by 50%. Child-Pugh C: Reduce dose by 75% or avoid use.
30-50 mg/kg/day orally divided every 6 hours; maximum 2 g/day.
30-50 mg/kg/day orally in divided doses every 6 hours, as ethylsuccinate. 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, but monitor for ototoxicity and QT prolongation. Initiate at lower end of dosing range.
E-MYCIN does not have a black box warning.
Increased risk of infantile hypertrophic pyloric stenosis (IHPS) when used in neonates; use only when no alternative therapy is available.
["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"]
Potential for QT prolongation and torsades de pointes, especially in patients with electrolyte disturbances or concurrent use of other QT-prolonging drugs; hepatic impairment; myasthenia gravis worsening; superinfection; risk of IHPS in neonates; caution in renal impairment.
["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 CYP3A4 substrates that prolong QT interval (e.g., cisapride, pimozide, ergotamine) due to risk of 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.
Administration with food may reduce gastrointestinal adverse effects. Grapefruit and grapefruit juice should be avoided as they inhibit CYP3A4 and can increase erythromycin levels, raising risk of QT prolongation and other adverse effects. Avoid alcohol as it may exacerbate GI irritation.
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 (E.E.S. 200) is classified as FDA Pregnancy Category B. Animal reproduction studies have not demonstrated fetal risk, but no adequate human studies exist. First trimester: No teratogenic effects reported; however, use only if clearly needed. Second and third trimesters: Considered safe; no known fetal toxicity. There is a potential association with pyloric stenosis in neonates if used after 32 weeks gestation, though absolute risk is low. Overall risk-benefit assessment should consider maternal infection treatment necessity.
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 breast milk in small amounts. The milk-to-plasma ratio (M/P) is approximately 0.5. Oral absorption by the infant is minimal, and adverse effects are rare. However, there is a theoretical risk of infant gastrointestinal disturbance or allergic reaction. The American Academy of Pediatrics considers erythromycin compatible with breastfeeding. Caution is advised, especially in infants with jaundice or hepatic impairment.
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).
Pregnancy induces physiological changes including increased plasma volume, renal blood flow, and hepatic metabolism. Erythromycin pharmacokinetics in pregnancy: decreased peak serum concentrations (Cmax) by 20-30%, increased volume of distribution, but no significant change in half-life. The area under the curve (AUC) may be reduced. Standard dosing (250-500 mg every 6 hours) is usually sufficient; however, severe infections may require higher doses or additional monitoring of therapeutic levels. No routine dose adjustment is recommended, but clinical response should be evaluated.
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 ethylsuccinate is a macrolide antibiotic with similar spectrum to penicillin. It is a CYP3A4 inhibitor; monitor for interactions with statins, warfarin, and other CYP3A4 substrates. QT prolongation risk; avoid with other QT-prolonging drugs. Use with caution in hepatic impairment. Common GI adverse effects may be mitigated by administration with food. It is pregnancy category B.
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, even if you feel better.Complete the full course of therapy to prevent resistance.May cause nausea, vomiting, abdominal pain, or diarrhea. Taking with food may reduce GI upset.Inform your doctor if you have liver disease, heart rhythm problems, or are taking other medications.Avoid grapefruit and grapefruit juice while on this medication due to potential interaction.Report any signs of allergic reaction (rash, hives, difficulty breathing) or severe diarrhea (watery or bloody stools).