ERYTHROCIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ERYTHROCIN (ERYTHROCIN).
Erythromycin is a macrolide antibiotic that binds to the 50S subunit of the bacterial ribosome, inhibiting protein synthesis by blocking translocation of peptidyl-tRNA. It also exhibits anti-inflammatory and prokinetic effects via motilin receptor agonism.
| Metabolism | Primarily metabolized by CYP3A4 isoenzyme in the liver; undergoes demethylation and N-demethylation; major metabolite is N-desmethylerythromycin. |
| Excretion | Primarily eliminated via biliary excretion as unchanged drug and metabolites; approximately 2-5% excreted renally as active drug, 15-20% as metabolites; up to 30% excreted in feces. |
| Half-life | Terminal elimination half-life is approximately 1.5-2 hours in adults; may prolong to 4-6 hours in hepatic impairment or neonates. |
| Protein binding | Approximately 70-90% bound, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd approximately 0.6-0.9 L/kg, indicating distribution into total body water and tissues; higher in children (0.8-1.2 L/kg). |
| Bioavailability | Oral: 30-65% (variable due to acid lability; enhanced by enteric coating); intramuscular: 70-80%; intravenous: 100%. |
| Onset of Action | Oral: 1-2 hours; intravenous: immediate (within minutes); topical: delayed, clinical effect seen within 2-3 weeks for acne. |
| Duration of Action | Oral and intravenous: 6-12 hours (bacteriostatic action persists while concentrations above MIC); topical: continuous with daily application. |
| Molecular Weight | 733.93 |
| Action Class | Macrolides |
| Brand Substitutes | Erythromycin Estol 500mg Tablet, Eryster 500mg Tablet, Eltocin 500mg Tablet, Erytho 500mg Tablet, Elucin 500mg Tablet, Agrocin 250mg Tablet, Eryster 250mg Tablet, Erythrokem 250mg Tablet, Erythrotone 250mg Tablet, E Mycin 250mg Tablet, Ticin Suspension, Ortholate Suspension, E Mycin 100mg Suspension, Methro Suspension, Althrocin 100mg Tablet, Ortholate 100mg Tablet, T Mycin 100mg Tablet, Erocin 100mg Tablet |
250-500 mg orally every 6 hours or 500 mg to 1 g intravenously every 6 hours.
| Dosage form | INJECTABLE |
| Renal impairment | Erythromycin is primarily hepatically eliminated; no dose adjustment required for renal impairment, but caution in severe renal failure (CrCl <10 mL/min) due to potential ototoxicity. |
| Liver impairment | In Child-Pugh class A: usual dose; class B: reduce dose by 50% or extend interval; class C: avoid or use with extreme caution with 75% dose reduction. |
| Pediatric use | 30-50 mg/kg/day orally divided every 6 hours, or 20-40 mg/kg/day intravenously divided every 6 hours; maximum 2 g/day. |
| Geriatric use | No specific dose adjustment; use caution due to increased risk of QT prolongation and hearing loss; monitor electrolytes and ECG. |
| 1st trimester | Erythromycin is generally considered safe during the first trimester. Studies have not shown an increased risk of major birth defects. However, use only if clearly needed due to potential for maternal benefit. |
| 2nd trimester | Safe for use in the second trimester. No evidence of teratogenic effects. Monitor for maternal gastrointestinal intolerance. |
| 3rd trimester | Safe for use in the third trimester. No known adverse fetal effects. Risk of maternal QT prolongation is low but consider ECG monitoring if used with other QT-prolonging drugs. |
Clinical note
Comprehensive clinical and safety monograph for ERYTHROCIN (ERYTHROCIN).
| Placental transfer | Erythromycin crosses the placenta with fetal serum levels approximately 5-20% of maternal levels. Higher transfer occurs at term and with higher maternal doses. |
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts. It is generally considered compatible with breastfeeding. However, in infants, oral use of erythromycin has been associated with infantile hypertrophic pyloric stenosis when used early in life. Monitor infant for potential gastrointestinal effects and rare hypersensitivity reactions. |
■ FDA Black Box Warning
Erythromycin may prolong the QT interval and increase the risk of ventricular arrhythmias, including torsades de pointes, especially in patients with pre-existing QT prolongation, electrolyte disturbances, or concomitant use of other QT-prolonging drugs.
| Serious Effects |
Hypersensitivity to erythromycin or any macrolide antibioticPre-existing QT interval prolongation or history of torsades de pointesConcurrent use with cisapride, pimozide, ergotamine, or dihydroergotamine (increased risk of cardiotoxicity)Use of erythromycin with statins metabolized by CYP3A4 (e.g., lovastatin, simvastatin) due to increased risk of rhabdomyolysis
| Precautions | QT prolongation and risk of arrhythmias; hepatotoxicity (elevated liver enzymes, cholestatic hepatitis); exacerbation of myasthenia gravis; increased risk of pyloric stenosis in neonates (oral use); Clostridioides difficile-associated diarrhea; drug interactions via CYP3A4 inhibition (e.g., statins, warfarin, ergotamine). |
| Food/Dietary | Grapefruit juice increased erythromycin AUC by 49%; avoid concurrent consumption. Food delays absorption but does not reduce total absorption; take with food if gastrointestinal intolerance occurs. |
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| Lactation Rating | L1 (Compatible) |
| Teratogenic Risk | Category B: No evidence of teratogenicity in animal studies; limited human studies show no increased risk of major malformations. Fetal risk cannot be excluded but appears low. Use only if clearly needed. |
| Fetal Monitoring | Maternal: Assess for gastrointestinal intolerance, QT prolongation (especially with electrolyte disturbances or concurrent QT-prolonging drugs), hepatotoxicity, and allergic reactions. Fetal: Non-stress test or biophysical profile if used for preterm premature rupture of membranes to monitor for chorioamnionitis; no specific fetal monitoring for drug toxicity required. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment of fertility at therapeutic doses. |
| Clinical Pearls | Erythromycin is a macrolide antibiotic with prokinetic properties, useful for gastroparesis. It is a CYP3A4 inhibitor; avoid coadministration with statins (except pravastatin, rosuvastatin), colchicine, and ergot alkaloids. QT prolongation risk; monitor ECG in patients with electrolyte abnormalities, bradycardia, or concurrent QT-prolonging drugs. IV administration can cause thrombophlebitis; dilute and rotate sites. |
| Patient Advice | Take exactly as prescribed; finish the entire course even if you feel better. · Do not crush or chew delayed-release tablets; swallow whole. · Avoid grapefruit juice during therapy (increases drug levels). · Take with or without food; if stomach upset occurs, take with food. · Contact your doctor if you experience severe diarrhea, irregular heartbeat, or hearing loss. · Report symptoms of liver problems: dark urine, yellowing skin/eyes, abdominal pain. |