ILOSONE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ILOSONE (ILOSONE).
Erythromycin (ILOSONE) binds to the 50S subunit of bacterial ribosomes, inhibiting peptide chain elongation and protein synthesis by blocking translocation.
| Metabolism | Primarily hepatic via CYP3A4; undergoes demethylation and hydroxylation. Excreted mainly in bile, with some renal elimination. |
| Excretion | Renal (2-5% unchanged), biliary/fecal (majority, >90% as metabolites and unchanged drug) |
| Half-life | 1.5-2 hours in adults; prolonged in hepatic impairment (up to 5-6 hours) |
| Protein binding | 70-90% bound to alpha-1-acid glycoprotein and albumin |
| Volume of Distribution | 0.5-0.7 L/kg (approx. 35-49 L in 70 kg adult); indicates tissue penetration |
| Bioavailability | Oral: 30-65% (variable due to acid lability; estolate form has higher absorption) |
| Onset of Action | Oral: 1-2 hours; IV: rapid (within 30 minutes) |
| Duration of Action | 6-12 hours for susceptible organisms; clinical effect may persist longer |
Erythromycin (Ilosone) base or stearate: 250-500 mg orally every 6 hours. Estolate: 250-500 mg orally every 6 hours. Maximum dose 4 g/day.
| Dosage form | SUSPENSION |
| Renal impairment | No dose adjustment required for GFR ≥10 mL/min. For GFR <10 mL/min, reduce dose by 50% or extend interval to every 8-12 hours. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: reduce dose by 75% or avoid use. |
| Pediatric use | 30-50 mg/kg/day orally divided every 6 hours. Maximum 2 g/day. For estolate: 30-50 mg/kg/day divided every 6-8 hours. |
| Geriatric use | Increased risk of QT prolongation and torsades de pointes. Use lower end of dosing range (250 mg orally every 6 hours) and monitor electrolytes and ECG. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ILOSONE (ILOSONE).
| Breastfeeding | Excreted into breast milk in small amounts; M/P ratio not established. Considered compatible with breastfeeding by the American Academy of Pediatrics. Monitor infant for diarrhea or rash. |
| Teratogenic Risk | Pregnancy Category B. No evidence of teratogenicity in animal studies; inadequate human data. Generally considered safe in all trimesters, although cautious use advised due to potential for gastrointestinal disturbances. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to erythromycin or any macrolide antibiotic","Concurrent use with ergotamine or dihydroergotamine (acute ergot toxicity)","Use with cisapride, pimozide, or terfenadine (risk of cardiotoxicity)","Hepatic dysfunction (relative contraindication for estolate salt)"]
| Precautions | ["QT interval prolongation and risk of torsades de pointes, especially with concomitant use of other QT-prolonging drugs or in patients with electrolyte abnormalities","Hepatotoxicity, including cholestatic hepatitis, particularly with estolate salt","Exacerbation of myasthenia gravis symptoms","Increased risk of infantile hypertrophic pyloric stenosis in neonates exposed to erythromycin","Clostridium difficile-associated diarrhea","Potential for drug interactions due to CYP3A4 inhibition"] |
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| No specific monitoring required. Routine prenatal care. Observe for maternal adverse effects (e.g., hepatotoxicity, QT prolongation). |
| Fertility Effects | No known adverse effects on fertility in males or females. |