E-MYCIN E
Clinical safety rating: caution
Comprehensive clinical and safety monograph for E-MYCIN E (E-MYCIN E).
Erythromycin binds to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis by blocking the translocation of peptide chains.
| Metabolism | Erythromycin is primarily metabolized by the hepatic cytochrome P450 enzyme system (CYP3A4) via demethylation. |
| Excretion | Primarily excreted unchanged in urine (70-80%) via glomerular filtration and tubular secretion; 15-20% excreted in feces via biliary elimination. |
| Half-life | Terminal elimination half-life is 1.5-3 hours in adults; prolonged to 4-6 hours in neonates and patients with hepatic impairment. |
| Protein binding | 70-80% bound, primarily to albumin. |
| Volume of Distribution | 0.6-0.9 L/kg; indicates extensive tissue penetration, including lung, tonsils, and middle ear fluid. |
| Bioavailability | Oral: 30-40% (erythromycin base is acid-labile); enteric-coated formulations: 40-60%. |
| Onset of Action | Oral: 30-60 minutes; intravenous: immediate (within minutes). |
| Duration of Action | 6-8 hours for susceptible organisms; clinical effect persists 8-12 hours post-dose. |
250-500 mg orally every 6 hours or 333-500 mg every 8 hours; maximum 4 g/day.
| Dosage form | SUSPENSION |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. For severe renal impairment (eGFR < 10 mL/min), reduce dose by 50% or extend interval to every 12-18 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment. Class B: reduce dose by 50% or extend interval. Class C: avoid use or reduce dose by 75% and monitor closely. |
| Pediatric use | 30-50 mg/kg/day orally divided every 6-8 hours; maximum 2 g/day. For severe infections, up to 75 mg/kg/day divided every 6 hours. |
| Geriatric use | Consider reduced renal function; monitor for QT prolongation and ototoxicity. Initiate at lower end of dosing range (250 mg every 6 hours) and titrate based on response and tolerance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for E-MYCIN E (E-MYCIN E).
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts (M/P ratio approximately 0.5-1.0). Breastfeeding is considered safe as concentrations are low and unlikely to cause adverse effects in the infant. However, caution is advised due to potential for gastrointestinal disturbances or sensitization. The AAP classifies erythromycin as compatible with breastfeeding. |
| Teratogenic Risk | E-MYCIN E (erythromycin) is classified as FDA Pregnancy Category B. No teratogenic effects have been demonstrated in animal studies, and adequate well-controlled studies in pregnant women have not shown fetal risk. However, data are limited; use during pregnancy only if clearly needed. First trimester: No evidence of increased risk of major malformations. Second and third trimesters: Considered safe; erythromycin is a first-line agent for Group B Streptococcus prophylaxis during labor. |
■ FDA Black Box Warning
Erythromycin has been associated with prolongation of the QT interval and rare cases of ventricular arrhythmias, including torsades de pointes, which can be fatal. Avoid use in patients with known QT prolongation, electrolyte abnormalities, or concurrent use of other QT-prolonging drugs.
| Serious Effects |
["Hypersensitivity to erythromycin or any macrolide antibiotic","Concurrent use with terfenadine, astemizole, or cisapride due to risk of cardiotoxicity","Preexisting QT prolongation or history of ventricular arrhythmias"]
| Precautions | ["QT interval prolongation and risk of cardiac arrhythmias","Hepatic dysfunction and hepatitis","Exacerbation of myasthenia gravis","Clostridium difficile-associated diarrhea","Allergic reactions including anaphylaxis","Superinfection with prolonged use"] |
| Food/Dietary | Take on an empty stomach: 1 hour before or 2 hours after meals. Avoid grapefruit juice as it can increase erythromycin serum concentrations and risk of QT prolongation. Avoid alcohol as it may increase hepatotoxicity risk. High-fat meals may delay absorption. |
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| Fetal Monitoring | No specific maternal-fetal monitoring is required beyond standard prenatal care. For prolonged use or high doses, monitor maternal liver function and hearing (ototoxicity risk with high doses). Fetal monitoring as per routine obstetrical care. |
| Fertility Effects | No known adverse effects on fertility in males or females. Erythromycin has not been associated with reduced fertility or impaired reproductive function in animal studies or human data. |
| Clinical Pearls | E-MYCIN E (erythromycin ethylsuccinate) is a macrolide antibiotic with bacteriostatic activity against gram-positive cocci and atypical pathogens. It is a prodrug that is hydrolyzed to active erythromycin. Administer on an empty stomach for optimal absorption. It may prolong QT interval; use with caution in patients with electrolyte disturbances or concurrent QT-prolonging drugs. Monitor for hepatotoxicity, especially in patients with pre-existing liver disease. It is a strong inhibitor of CYP3A4, increasing levels of statins, warfarin, and other drugs. |
| Patient Advice | Take this medication exactly as prescribed, usually every 6 to 8 hours, on an empty stomach (1 hour before or 2 hours after meals). · Do not crush or chew the tablets; swallow them whole with a full glass of water. · Complete the full course of therapy even if you feel better to prevent antibiotic resistance. · Avoid grapefruit juice as it may increase the effects and side effects of this medication. · Contact your doctor immediately if you experience jaundice, dark urine, severe abdominal pain, or signs of liver problems. · Inform your doctor about all medications you are taking, especially statins, warfarin, or other drugs metabolized by CYP3A4. · Use effective contraception if you are of childbearing age; this medication may reduce the effectiveness of hormonal contraceptives. · If you miss a dose, take it as soon as you remember. If it is almost time for the next dose, skip the missed dose and continue your regular schedule. Do not double the dose. |