ERYC
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ERYC (ERYC).
Erythromycin acts by binding to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis by blocking the translocation step.
| Metabolism | Primarily metabolized by the liver via CYP3A4. Metabolites include N-desmethylerythromycin and other derivatives. |
| Excretion | Primarily biliary excretion of unchanged drug (60–80%); renal excretion accounts for 10–15% of an oral dose, with minimal fecal elimination (<5%). |
| Half-life | 2–4 hours in adults with normal renal function; prolonged to 4–8 hours in severe hepatic impairment; does not significantly change in renal failure. |
| Protein binding | 70–90% bound, primarily to alpha-1-acid glycoprotein (AAG) and albumin. |
| Volume of Distribution | 0.6–1.2 L/kg (total body water and intracellular distribution); higher in tissue (e.g., lungs, liver) than plasma. |
| Bioavailability | Oral base: 25–45% (fasting); estolate: 60–80% (increased food effect); IV: 100%. |
| Onset of Action | Oral: 1–2 hours (base); 30–60 minutes (estolate); IV: within minutes; topical: variable (days to weeks for acne). |
| Duration of Action | Oral: 6–12 hours (base); IV: 6–8 hours; topical: sustained with daily application. |
| Molecular Weight | 733.93 |
250-500 mg orally every 6 hours or 333-500 mg orally every 8 hours; maximum 4 g/day.
| Dosage form | CAPSULE, DELAYED REL PELLETS |
| Renal impairment | No adjustment required for mild-to-moderate renal impairment. For CrCl <10 mL/min, reduce dose by 50% or increase dosing interval to every 12-24 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 50%. Child-Pugh Class C: avoid use or reduce dose by 75% with close monitoring. |
| Pediatric use | Neonates: 7.5-15 mg/kg orally every 8-12 hours. Infants and children: 15-25 mg/kg orally every 6 hours (maximum 2 g/day). |
| Geriatric use | No specific dose adjustment based on age alone, but increased risk of adverse effects (e.g., QT prolongation, GI intolerance). Use lowest effective dose and monitor renal function. |
| 1st trimester | Use only if clearly needed; erythromycin has been associated with a small increased risk of cardiovascular malformations in some studies, but data are conflicting. Consider benefits vs risks. |
| 2nd trimester | Generally considered safe; no known teratogenic effects in second trimester. |
| 3rd trimester | Use near term with caution due to risk of infantile hypertrophic pyloric stenosis (IHPS) if used after 32 weeks or during lactation. |
Clinical note
Comprehensive clinical and safety monograph for ERYC (ERYC).
| Placental transfer | Erythromycin crosses the placenta variably; fetal concentrations are approximately 10-20% of maternal serum levels. |
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts (milk:plasma ratio ~0.5-1.0). It is generally considered compatible with breastfeeding, but caution in infants with biliary tract disease or hepatic impairment. Reported risk of IHPS in infants exposed via breast milk is very low but may occur, especially in first 2 months of life. |
■ FDA Black Box Warning
Increased risk of infantile hypertrophic pyloric stenosis (IHPS) when used in neonates. Concomitant use with strong CYP3A4 inhibitors (e.g., ketoconazole) may increase risk of QT prolongation and sudden cardiac death.
| Serious Effects |
Hypersensitivity to erythromycin or any macrolide antibioticConcomitant use with cisapride, pimozide, ergotamine, or dihydroergotamine (risk of QT prolongation and cardiac arrhythmias)Concomitant use with HMG-CoA reductase inhibitors (statins) that are CYP3A4 substrates (e.g., lovastatin, simvastatin) due to increased risk of myopathy/rhabdomyolysis
| Precautions | QT prolongation and risk of torsades de pointes, especially with electrolyte abnormalities or concurrent use of QT-prolonging drugs. Hepatotoxicity (cholestatic hepatitis) mainly with erythromycin estolate. Clostridium difficile-associated diarrhea. Myasthenia gravis exacerbation. Avoid in neonates due to IHPS risk. |
| Food/Dietary | Avoid grapefruit juice. Take ERYC on an empty stomach (1 hour before or 2 hours after meals) to enhance absorption. Food decreases absorption; high-fat meals may delay absorption. |
Loading safety data…
| Lactation Rating | L2 (Limited data - probably compatible) |
| Teratogenic Risk | FDA Category B. No evidence of teratogenicity in human studies; limited data in first trimester suggests no increased risk of major malformations. Second and third trimester use is considered safe. |
| Fetal Monitoring | No specific fetal monitoring required. Monitor maternal gastrointestinal tolerance and signs of hepatotoxicity or QT prolongation with high doses. |
| Fertility Effects | No known adverse effects on fertility or reproductive function in animal studies; no human data available. |
| Clinical Pearls | ERYC (erythromycin) is a macrolide antibiotic with prokinetic properties; use caution in patients with prolonged QT interval. It is a substrate of CYP3A4 and an inhibitor of CYP3A4, leading to numerous drug interactions. Administer on an empty stomach 1 hour before or 2 hours after meals for optimal absorption. Erythromycin can cause infantile hypertrophic pyloric stenosis when given to neonates; avoid use in this population. |
| Patient Advice | Take ERYC exactly as prescribed, at evenly spaced intervals. · Do not skip doses; complete the full course even if you feel better. · Avoid grapefruit juice while taking ERYC as it may increase drug levels. · Report any signs of liver problems (yellowing skin/eyes, dark urine) or irregular heartbeat. · Inform your doctor about all medications you take, including over-the-counter drugs and supplements. · If you experience severe diarrhea or watery stools, contact your doctor immediately. |