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 |
| Molecular Weight | 733.93 |
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 | Use is generally avoided due to potential fetal effects; no well-controlled studies. Erythromycin estolate is associated with increased risk of hepatotoxicity in pregnant women. |
| 2nd trimester | Use only if clearly needed. Crosses placenta; limited data suggest no major teratogenic risk, but caution advised. |
| 3rd trimester | Use only if clearly needed. May be used for Group B Streptococcus prophylaxis if penicillin-allergic. Risk of infantile hypertrophic pyloric stenosis (IHPS) if used near term. |
Clinical note
Comprehensive clinical and safety monograph for ILOSONE (ILOSONE).
| Placental transfer | Crosses the placenta; fetal serum levels reach 5-20% of maternal levels. Higher transfer with estolate salt. |
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts. Risk of infantile hypertrophic pyloric stenosis (IHPS) in infants exposed via breast milk, especially in first 2 weeks of life. Monitoring for infant gastrointestinal symptoms recommended. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to erythromycin or any componentPre-existing liver disease or hepatic impairmentConcurrent use with cisapride, pimozide, ergotamine, or lovastatin
| 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 |
| Food/Dietary | Grapefruit and grapefruit juice should be avoided as they inhibit CYP3A4 and may increase erythromycin levels, raising the risk of adverse effects including QT prolongation. High-fat meals may decrease absorption; take on an empty stomach for best effect. |
Loading safety data…
| Lactation Rating | L2 (Limited data - possibly safe) |
| 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 | 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. |
| Clinical Pearls | Ilosone (erythromycin estolate) is a macrolide antibiotic with a high risk of hepatotoxicity, especially in adults; avoid use in patients with pre-existing liver disease. It is a CYP3A4 inhibitor and can increase levels of statins, warfarin, and other drugs metabolized by this enzyme. Due to QT prolongation risk, avoid concurrent use with other QT-prolonging agents. Administer on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption, though food may reduce GI upset. |
| Patient Advice | Take this medication exactly as prescribed; do not skip doses or stop early even if you feel better. · Take on an empty stomach (1 hour before or 2 hours after meals) with a full glass of water. · Avoid alcohol while taking this medication due to increased risk of liver damage. · Notify your doctor immediately if you experience yellowing of skin or eyes, dark urine, severe stomach pain, or unusual fatigue (signs of liver problems). · This drug may cause diarrhea; do not treat with anti-diarrheal medications without consulting your doctor. · Inform your doctor of all other medications you are taking, including over-the-counter drugs and herbal supplements. · Avoid grapefruit and grapefruit juice as they may increase side effects. |