ERY-TAB
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ERY-TAB (ERY-TAB).
Erythromycin binds to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis by blocking the translocation step.
| Metabolism | Primarily metabolized by CYP3A4 in the liver; also metabolized via demethylation. Erythromycin is a substrate and inhibitor of CYP3A4. |
| Excretion | Erythromycin is primarily excreted in bile as active drug and metabolites, with approximately 12-15% of an administered dose excreted unchanged in urine. Fecal elimination accounts for about 30-60% of the dose, largely due to biliary excretion. |
| Half-life | The terminal elimination half-life of erythromycin base is approximately 1.5-2 hours in patients with normal renal function. In patients with end-stage renal disease, the half-life may be prolonged to 4-6 hours. The half-life is not significantly altered in hepatic impairment, but accumulation can occur with severe liver disease. |
| Protein binding | Erythromycin is approximately 70-90% bound to plasma proteins, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | The apparent volume of distribution (Vd) for erythromycin is approximately 0.6-0.9 L/kg, indicating distribution into total body water with penetration into tissues and cells. |
| Bioavailability | The oral bioavailability of erythromycin base (as ERY-TAB) is approximately 30-65% due to acid instability and first-pass metabolism. The enteric-coated tablet formulation improves bioavailability compared to uncoated forms. |
| Onset of Action | For oral administration of erythromycin base (e.g., ERY-TAB), onset of action typically occurs within 1-2 hours following a dose. For intravenous administration, onset is more rapid, within 30 minutes. |
| Duration of Action | The duration of antibacterial action for erythromycin is approximately 6-12 hours for susceptible organisms, depending on dose and route. For typical dosing regimens (e.g., 250 mg every 6 hours), therapeutic levels are maintained for the dosing interval. |
| Molecular Weight | 733.93 |
250-500 mg orally every 6 hours or 333-666 mg every 8 hours. Maximum 4 g/day.
| Dosage form | TABLET, DELAYED RELEASE |
| Renal impairment | No adjustment required for mild to moderate renal impairment. For severe renal impairment (CrCl <10 mL/min), maximum dose 2 g/day. Not significantly removed by hemodialysis or CAPD. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: reduce dose by 75% or consider alternative. |
| Pediatric use | Neonates: 10 mg/kg/dose every 12 hours (postnatal age ≤7 days) or every 8 hours (8-28 days). Infants and children: 10-15 mg/kg/dose every 6 hours, maximum 2 g/day. |
| Geriatric use | Use lower end of dosing range (250 mg every 6 hours). Monitor for QT prolongation and hearing loss. Consider age-related renal function decline. |
| 1st trimester | No evidence of fetal harm in animal studies; however, use only if clearly needed. Safety in human pregnancy not established. |
| 2nd trimester | Use cautiously, as erythromycin estolate is associated with maternal hepatotoxicity; ERY-TAB (erythromycin base) is preferred if macrolide needed. |
| 3rd trimester | Generally considered safe; no known risk of fetal harm. Use for Group B Streptococcus prophylaxis in penicillin-allergic patients. |
Clinical note
Comprehensive clinical and safety monograph for ERY-TAB (ERY-TAB).
| Placental transfer | Crosses the placenta; fetal serum concentrations reach 5-20% of maternal levels. |
| Breastfeeding | Erythromycin is excreted into breast milk in small amounts. The American Academy of Pediatrics considers it compatible with breastfeeding. Monitor infant for gastrointestinal disturbances. |
■ FDA Black Box Warning
WARNING: Increased risk of infantile hypertrophic pyloric stenosis (IHPS) following erythromycin use in neonates. Also, QT prolongation and increased risk of sudden cardiac death with concurrent use of CYP3A4 inhibitors or other QT-prolonging drugs.
| Serious Effects |
Hypersensitivity to erythromycin or any macrolide antibioticConcurrent use with ergotamine or dihydroergotamineConcurrent use with HMG-CoA reductase inhibitors (statins) metabolized by CYP3A4 (e.g., simvastatin, lovastatin)Pre-existing liver disease with elevated liver enzymes
| Precautions | QT prolongation and ventricular arrhythmias, including torsades de pointes, especially with concurrent use of other QT-prolonging drugs or in patients with electrolyte abnormalities., Hepatotoxicity, particularly with erythromycin estolate., Clostridium difficile-associated diarrhea (CDAD)., Myasthenia gravis exacerbation., Infantile hypertrophic pyloric stenosis in neonates. |
| Food/Dietary | Avoid grapefruit juice; it may increase erythromycin levels. High-fat meals may delay absorption but not reduce extent; consistent timing relative to meals is recommended. |
Loading safety data…
| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | Erythromycin base (ERY-TAB) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated teratogenic effects. Human data from large cohort studies and meta-analyses do not show a significantly increased risk of major congenital malformations following first-trimester exposure. However, an association with pyloric stenosis in neonates exposed during late pregnancy or after birth has been reported, though absolute risk remains low. No specific fetal risks are documented for second or third trimester use. |
| Fetal Monitoring | No specific fetal monitoring is required. For maternal use, monitor for hepatotoxicity (liver function tests) and QT prolongation (ECG) in patients at risk. In neonates exposed in utero, observe for signs of hypertrophic pyloric stenosis (projectile vomiting, irritability) in the first few weeks of life, especially if exposure occurred after 20 weeks gestation. |
| Fertility Effects | Erythromycin has no established direct effects on human fertility. In animal studies, no impairment of fertility was observed at clinically relevant doses. No specific data on spermatogenesis or ovulatory function are available. |
| Clinical Pearls | ERY-TAB (erythromycin base) is a macrolide antibiotic; absorption is enhanced when taken on an empty stomach, but food does not significantly affect bioavailability. It is a cytochrome P450 3A4 inhibitor; monitor for drug interactions with statins, warfarin, and other CYP3A4 substrates. Prolongs QT interval; use with caution in patients with electrolyte abnormalities or other QT-prolonging drugs. May cause gastrointestinal distress; consider dose titration or adjunctive therapy. |
| Patient Advice | Take this medication exactly as prescribed, even if you feel better. · Swallow tablets whole; do not crush, chew, or break. · If stomach upset occurs, take with food or milk. · Complete the full course to prevent resistance. · Report any signs of liver issues (yellowing skin/eyes, dark urine) or hearing loss. |