Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ERYC 125 vs A/T/S
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Erythromycin binds to the 50S subunit of bacterial ribosomes, inhibiting protein synthesis by blocking translocation of peptidyl-t RNA. It also activates motilin receptors in the gastrointestinal tract, enhancing gastric motility.
A/T/S (erythromycin) is a macrolide antibiotic that acts by binding to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis and bacterial growth.
Treatment of infections caused by susceptible strains of microorganisms (e.g., respiratory tract infections, skin infections, pertussis, diphtheria, syphilis),Off-label: Prokinetic agent for gastroparesis, treatment of delayed gastric emptying
Treatment of acne vulgaris (FDA-approved indication),Treatment of bacterial infections caused by susceptible organisms (off-label use for acne is the primary use)
250 mg orally every 6 hours or 500 mg every 12 hours; maximum 4 g/day.
Dosing is individualized based on antithrombin activity level. For acute thrombotic events: initial bolus of 30-50 IU/kg followed by maintenance dosing to achieve target activity levels (80-120% of normal). Prophylaxis: 40-60 IU/kg every 24 hours.
1.5-2.0 hours in adults; prolonged in hepatic impairment (up to 5-6 hours) or neonates.
Terminal elimination half-life: 1–2 hours (prolonged in hepatic impairment).
Primarily hepatic via cytochrome P450 3A4 (CYP3A4) isoenzyme; undergoes demethylation and hydrolysis; major metabolite is desosamine.
Antithrombin is a glycoprotein; its metabolism involves cellular uptake and catabolism, but specific CYP450 enzymes are not involved. Degradation occurs via proteolysis and reticuloendothelial system clearance.
Primarily hepatic metabolism; ~2-5% excreted unchanged in urine, ~15-20% in bile/feces as active drug.
Renal: 10-20% (active drug and metabolites); Fecal: minimal; Biliary: not significant.
70-90% bound to albumin and alpha-1-acid glycoprotein.
70-90% bound to serum albumin.
0.5-0.9 L/kg; indicates distribution into total body water with some tissue binding.
0.5–0.8 L/kg (low Vd, minimal tissue penetration).
Oral: ~35% (acid-labile, enteric-coated).
Topical: 1–5% (minimal systemic absorption).
No dose adjustment required for GFR >10 m L/min. For GFR <10 m L/min, reduce dose by 50% or extend interval to every 8-12 hours.
No specific adjustment required; drug is not renally eliminated.
Child-Pugh Class A: no adjustment. Class B: reduce dose by 50%. Class C: reduce dose by 75% or avoid use.
No specific adjustment; antithrombin is produced in the liver, but exogenous replacement does not require dose adjustment in hepatic impairment.
30-50 mg/kg/day orally divided every 6-8 hours; maximum 2 g/day.
Dosing based on weight and antithrombin levels; typical initial dose 30-50 IU/kg, followed by maintenance to achieve target levels. Clinical trial data limited in neonates.
No specific adjustment; monitor for ototoxicity and QT prolongation; consider lower initial dose due to age-related renal decline.
No specific adjustment; use standard dosing with monitoring of antithrombin activity and bleeding risk.
No FDA boxed warning for ERYC 125.
None.
Risk of QT prolongation and ventricular arrhythmias (e.g., torsades de pointes), especially with other QT-prolonging drugs or electrolyte abnormalities,Hepatic impairment: monitor liver function,Potential for drug interactions via CYP3A4 inhibition,May exacerbate myasthenia gravis,Infantile hypertrophic pyloric stenosis (IHPS) risk in neonates
Hypersensitivity reactions including anaphylaxis have occurred.,Prolonged use may result in overgrowth of nonsusceptible organisms including fungi.,Use with caution in patients with hepatic impairment.,Potential for QT prolongation and ventricular arrhythmias, especially with intravenous administration or concomitant drugs that prolong QT interval.
Hypersensitivity to erythromycin or any macrolide antibiotic,Concomitant use with CYP3A4 substrates that prolong QT interval (e.g., terfenadine, astemizole, cisapride, pimozide),Pre-existing QT prolongation or cardiac arrhythmia history
Hypersensitivity to erythromycin or any macrolide antibiotic.,Use with caution in patients with pre-existing QT prolongation or electrolyte abnormalities (relative contraindication).
Grapefruit and grapefruit juice should be avoided as they can increase drug levels and risk of toxicity. Food does not significantly alter absorption of the ethylsuccinate formulation, but taking with a high-fat meal may slightly delay absorption. Avoid alcohol as it may increase risk of hepatotoxicity.
No specific food interactions. Avoid excessive alcohol consumption as it may increase skin dryness.
Erythromycin, including ERYC 125, has not been associated with major congenital malformations in human studies. However, there is a potential increased risk of pyloric stenosis in infants exposed in utero or postnatally. No known teratogenic effects in first trimester; use in pregnancy is generally considered safe when indicated, especially for infections like chlamydia or syphilis.
FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; no adequate human studies in first trimester. Topical erythromycin has minimal systemic absorption; risk to fetus is low across all trimesters.
Erythromycin is excreted into breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.5. It is considered compatible with breastfeeding by the American Academy of Pediatrics, but may increase the risk of pyloric stenosis in neonates. Monitor for gastrointestinal symptoms in the infant.
Compatible with breastfeeding. Erythromycin is excreted into breast milk in small amounts (M/P ratio approximately 0.5). Topical use results in negligible systemic exposure; unlikely to cause adverse effects in nursing infants.
No specific dose adjustment is required for pregnancy based on pharmacokinetic changes. However, erythromycin has reduced plasma concentrations in late pregnancy due to increased volume of distribution and clearance, but no dose adjustment is recommended. Standard dosing is used.
No dose adjustment required. Systemic absorption from topical application is minimal and not significantly altered by pregnancy-related pharmacokinetic changes.
ERYC 125 (erythromycin ethylsuccinate) is a macrolide antibiotic; note that it may prolong QT interval, especially when combined with other QT-prolonging drugs. Avoid use in patients with hepatic impairment or known cholestatic jaundice. Administer on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption, but food does not significantly affect the ethylsuccinate formulation.
A/T/S (erythromycin 2% topical solution) is indicated for acne vulgaris. Avoid contact with eyes, mouth, and mucous membranes. May cause skin dryness or irritation; use moisturizer. Effectiveness may decrease with prolonged use due to bacterial resistance. Not recommended for use with other topical erythromycin products or clindamycin to avoid antagonism.
Take exactly as prescribed; do not skip doses or stop early even if you feel better.,Take this medication on an empty stomach, at least 1 hour before or 2 hours after a meal.,Avoid grapefruit and grapefruit juice while taking this medicine.,Report any signs of liver problems: yellowing of skin/eyes, dark urine, severe stomach pain.,Notify your doctor immediately if you experience irregular heartbeat, fainting, or severe diarrhea.,Complete the full course to prevent antibiotic resistance.
Apply a thin layer to affected areas twice daily after washing.,Avoid contact with eyes, lips, and mouth; if contact occurs, rinse thoroughly with water.,May cause stinging, burning, or peeling; if irritation persists, consult your doctor.,Use sunscreen daily as this medication may increase sensitivity to sunlight.,Do not use more than prescribed; overuse may increase side effects without improving results.,Inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding.,Keep away from open flames or heat sources; product is flammable.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ERYC 125 vs A/T/S, answered by our medical review team.
ERYC 125 is a Macrolide Antibiotic that works by Erythromycin binds to the 50S subunit of bacterial ribosomes, inhibiting protein synthesis by blocking translocation of peptidyl-t RNA. It also activates motilin receptors in the gastrointestinal tract, enhancing gastric motility.. A/T/S is a Macrolide antibiotic that works by A/T/S (erythromycin) is a macrolide antibiotic that acts by binding to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis and bacterial growth.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ERYC 125 and A/T/S depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ERYC 125 is: 250 mg orally every 6 hours or 500 mg every 12 hours; maximum 4 g/day.. The standard adult dose of A/T/S is: Dosing is individualized based on antithrombin activity level. For acute thrombotic events: initial bolus of 30-50 IU/kg followed by maintenance dosing to achieve target activity levels (80-120% of normal). Prophylaxis: 40-60 IU/kg every 24 hours.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between ERYC 125 and A/T/S in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. ERYC 125 is classified as Category C. Erythromycin, including ERYC 125, has not been associated with major congenital malformations in human studies. However, there is a potential increased risk of pyloric stenosis in . A/T/S is classified as Category C. FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; no adequate human studies in first trimester. Topical erythromycin has minimal systemic absorption; risk . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.