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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ERYC (ERYC).
| Breastfeeding | Excreted into breast milk in small amounts (M/P ratio ~0.5). Considered compatible with breastfeeding; monitor infant for gastrointestinal disturbances. |
| 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 |
■ 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. Concomitant use with ergotamine or vasoconstrictive ergot alkaloids due to ergotism risk. Pre-existing QT prolongation or history of torsades de pointes. Use with strong CYP3A4 inhibitors (e.g., ritonavir, ketoconazole) is cautioned.
| 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. |
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| 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. |