ERYMAX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ERYMAX (ERYMAX).
Erythromycin acts by binding to the 50S subunit of the bacterial ribosome, inhibiting protein synthesis. It also acts as a motilin receptor agonist, stimulating gastrointestinal motility.
| Metabolism | Primarily metabolized by the liver via CYP3A4 enzyme system. Erythromycin is a substrate and inhibitor of CYP3A4. |
| Excretion | Renal excretion of unchanged drug: 10–15%; biliary/fecal excretion: 85–90% as active metabolites. |
| Half-life | Terminal elimination half-life: 1.5–2 hours in adults; prolonged to 4–6 hours in hepatic impairment; requires dosing adjustment in cirrhosis. |
| Protein binding | 75–85% bound primarily to albumin. |
| Volume of Distribution | 1.2–1.6 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: 50–60% (first-pass metabolism); IM: 80–90%; IV: 100%. |
| Onset of Action | Oral: 30–45 minutes; Intravenous: 5–10 minutes; Intramuscular: 15–30 minutes. |
| Duration of Action | 4–6 hours for most clinical effects; extended to 8–12 hours with sustained-release formulations. |
250-500 mg orally every 6 hours or 500-1000 mg intravenously every 6 hours.
| Dosage form | SOLUTION |
| Renal impairment | CrCl 10-50 mL/min: 250-500 mg every 6-12 hours; CrCl <10 mL/min: 250-500 mg every 12-24 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | 30-50 mg/kg/day orally divided every 6-8 hours; 20-40 mg/kg/day intravenously divided every 6 hours. |
| Geriatric use | Start at low end of dosing range (250 mg orally every 6 hours) and adjust based on renal function; monitor for QT prolongation and electrolyte disturbances. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ERYMAX (ERYMAX).
| Breastfeeding | Excreted in breast milk in low amounts (M/P ratio approximately 0.5). Considered compatible with breastfeeding; monitor infant for diarrhea or rash. |
| Teratogenic Risk | No evidence of teratogenicity in human studies; animal studies show no fetal harm at therapeutic doses. Risk Category B (FDA). First trimester: no increased malformation risk. Second/third trimester: no known adverse effects. |
| Fetal Monitoring |
■ FDA Black Box Warning
Increased risk of infantile hypertrophic pyloric stenosis (IHPS) when used in neonates and young infants.
| Serious Effects |
["Hypersensitivity to erythromycin or any macrolide antibiotic.","Concomitant use with ergotamine or dihydroergotamine (risk of ergotism).","Concomitant use with terfenadine, astemizole, or cisapride (risk of cardiotoxicity).","Pre-existing QT interval prolongation or history of torsades de pointes.","Hepatic impairment (for erythromycin estolate).","Neonates with known or suspected infantile hypertrophic pyloric stenosis."]
| Precautions | ["QT interval prolongation and risk of torsades de pointes, especially in patients with pre-existing QT prolongation, electrolyte imbalances, bradycardia, or concomitant use of other QT-prolonging drugs.","Hepatotoxicity, including cholestatic hepatitis, particularly with erythromycin estolate.","Clostridioides difficile-associated diarrhea (CDAD).","Exacerbation of myasthenia gravis.","Infantile hypertrophic pyloric stenosis (IHPS) in neonates.","Drug interactions due to CYP3A4 inhibition (e.g., with statins, warfarin, benzodiazepines).","Ototoxicity, especially with high doses or renal impairment."] |
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| No specific monitoring required; observe for maternal gastrointestinal effects. |
| Fertility Effects | No known adverse effects on fertility in animal or human studies. |