Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
E.E.S. 400 vs BIAXIN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Erythromycin, a macrolide antibiotic, binds to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis. At high concentrations, it may also inhibit RNA synthesis.
Binds to the 50S ribosomal subunit, inhibiting bacterial protein synthesis by blocking peptide chain elongation.
Treatment of infections caused by susceptible strains of microorganisms: respiratory tract infections (including Legionnaires disease, pertussis), skin and soft tissue infections, diphtheria, syphilis, chlamydial infections, and ocular infections in neonates.,Prophylaxis of recurrent rheumatic fever.,Off-label: gastrointestinal motility disorder (as a motilin agonist).
Acute bacterial exacerbation of chronic bronchitis,Acute maxillary sinusitis,Community-acquired pneumonia,Pharyngitis/tonsillitis,Uncomplicated skin and skin structure infections,Helicobacter pylori eradication (as part of triple or dual therapy),Mycobacterium avium complex prophylaxis and treatment (off-label for some indications)
Erythromycin ethylsuccinate 400 mg orally every 6 hours. For severe infections, up to 4 g/day in divided doses.
250-500 mg orally every 12 hours for 7-14 days; extended-release: 1000 mg orally every 24 hours for 7-14 days
1.5-2.0 hours in adults with normal renal function; may be prolonged in hepatic impairment (up to 5-6 hours) but not significantly changed in renal disease.
Terminal elimination half-life: 3-7 hours (single dose, 250-500 mg); with multiple dosing, half-life may extend to 7-10 hours due to saturable metabolism. Clinical context: Shorter half-life requires twice-daily dosing; extended half-life (via 14-hydroxy metabolite, t1/2 ~11 h) contributes to antibacterial activity.
Primarily metabolized in the liver via demethylation by CYP3A4; undergoes N-demethylation and hydroxylation.
Primarily metabolized by CYP3A4 isoenzyme; clarithromycin undergoes first-pass metabolism to form 14-hydroxyclarithromycin (active metabolite).
Primarily hepatic (biliary) excretion of unchanged drug and metabolites; approximately 2-5% renal excretion of unchanged drug; 5-15% fecal elimination.
Approximately 20-30% of administered dose is excreted unchanged in urine; remainder is hepatically metabolized and excreted in bile and feces (~50% fecal elimination).
70-80% bound to albumin; binding is reversible and saturable at high concentrations.
65-75% bound, primarily to albumin and alpha-1-acid glycoprotein.
Approximately 0.7 L/kg (range 0.5-0.9 L/kg); indicates extensive tissue penetration including intracellular and inflammatory fluids.
Vd: 2.6-3.5 L/kg. Clinical meaning: Large Vd indicates extensive tissue penetration, including lungs, tonsils, and sinuses, exceeding serum concentrations.
Oral (as erythromycin ethylsuccinate): approximately 30-65% (variable, reduced by food); intravenous: 100%.
Oral bioavailability: 50-55% (250 mg tablet); may be increased to 60-70% when administered with food. Intravenous: 100%.
No specific dose adjustment required for renal impairment; caution with high doses in severe renal failure (Cr Cl <10 m L/min) due to potential ototoxicity.
Cr Cl <30 m L/min: reduce dose by 50%; Cr Cl <10 m L/min: not recommended; no adjustment for Cr Cl >30 m L/min
In hepatic impairment, reduce dose by 50-75% depending on severity. Child-Pugh Class A: no adjustment; Class B: reduce to 50% of normal dose; Class C: avoid or use with extreme caution, maximum 1 g per day.
Child-Pugh Class C: reduce dose by 50% or consider alternative; mild to moderate hepatic impairment: no adjustment
30-50 mg/kg/day in 4 divided doses. For severe infections, up to 60-100 mg/kg/day. Maximum 2 g/day.
15 mg/kg/day orally divided every 12 hours; maximum 500 mg/day for 10 days; for extended-release, not recommended for children <12 years
No specific dose adjustment; monitor for QT prolongation and hearing loss. Consider lower end of dosing range due to age-related decline in hepatic function.
No specific dose adjustment; monitor renal function and adjust per renal guidelines; increased risk of QT prolongation
Increased risk of infantile hypertrophic pyloric stenosis (IHPS) when given to neonates. Erythromycin has also been associated with prolongation of the QT interval and risk of cardiac arrhythmias, including torsades de pointes.
None
Hepatic dysfunction, QT prolongation (risk of arrhythmia), exacerbation of myasthenia gravis, Clostridioides difficile-associated diarrhea, ototoxicity (especially with high doses or renal impairment), potential for drug interactions (CYP3A4 inhibitors/inducers).
Increased risk of cardiac arrhythmias, including QT prolongation and torsades de pointes; avoid in patients with known QT prolongation or concurrent use with QT-prolonging drugs.,Potential for hepatotoxicity (elevated liver enzymes, hepatitis); monitor liver function.,Exacerbation of myasthenia gravis symptoms.,Clostridioides difficile-associated diarrhea (CDAD).,Drug interactions via CYP3A4 inhibition (e.g., statins, warfarin, colchicine, and other macrolides).,Pregnancy Category C; avoid use unless no alternative (clarithromycin associated with increased risk of miscarriage and fetal abnormalities in animal studies).
Hypersensitivity to erythromycin or any macrolide antibiotic, concomitant use with terfenadine, astemizole, cisapride, pimozide, ergotamine, or dihydroergotamine (risk of cardiac arrhythmias).
Hypersensitivity to clarithromycin, erythromycin, or any macrolide antibiotic.,Concurrent use with pimozide, ergotamine, dihydroergotamine, lovastatin, simvastatin, or colchicine in renal/hepatic impairment.,History of cholestatic jaundice/hepatic dysfunction associated with prior clarithromycin use.,QT prolongation or history of ventricular arrhythmias (including torsades de pointes).,Concurrent use with antiarrhythmics (e.g., quinidine, procainamide, amiodarone) or other QT-prolonging drugs.,Severe hepatic failure or acute porphyria.
Take with food to minimize gastrointestinal upset. Avoid grapefruit juice as it can increase erythromycin concentrations via CYP3A4 inhibition. No other significant food interactions.
Grapefruit and grapefruit juice should be avoided as they inhibit CYP3A4 and may increase clarithromycin levels, raising risk of QT prolongation. High-fat meals may delay absorption but do not significantly alter total exposure. Alcohol is not specifically contraindicated but may increase gastrointestinal irritation; avoid concurrent use of statins (especially simvastatin, lovastatin) due to increased myopathy risk.
FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; inadequate human studies in first trimester. No known risk of major birth defects or miscarriage. Avoid in maternal myasthenia gravis due to potential neonatal hypotonia.
FDA Pregnancy Category C. Animal studies have shown fetal harm (cleft palate, skeletal abnormalities) at doses 2-5 times the human clinical dose. No adequate human studies. First trimester: Avoid unless benefit justifies risk. Second and third trimesters: Limited data; use only if clearly needed. Monitor for potential maternal hepatotoxicity.
Compatible with breastfeeding. Erythromycin is excreted into breast milk in small amounts (M/P ratio approximately 0.5). No adverse effects reported in infants. Monitor infant for gastrointestinal disturbances or rash.
Clarithromycin is excreted into human breast milk; the milk-to-plasma ratio is approximately 0.25-0.5. Infants exposed via breast milk may experience gastrointestinal disturbances or altered gut flora. Use with caution, especially in infants younger than 6 weeks of age due to risk of hypertrophic pyloric stenosis. Consider temporary discontinuation during therapy if high doses are used.
No dose adjustment required. Physiologic changes in pregnancy (increased volume of distribution, renal clearance) do not necessitate dose changes for erythromycin. Standard adult dosing applies.
No specific pharmacokinetic studies have demonstrated a need for dose adjustment during pregnancy. However, pregnancy can increase volume of distribution and renal clearance; empirical dose monitoring is not required. Standard dosing regimens are applied unless hepatic or renal impairment is present.
E. E. S. 400 (erythromycin ethylsuccinate) is a macrolide antibiotic with bacteriostatic activity. It is a prodrug hydrolyzed to erythromycin base. Use with caution in patients with hepatic impairment or preexisting hearing loss. Monitor for QT prolongation, especially with concurrent use of other QT-prolonging drugs. Commonly used as an alternative in penicillin-allergic patients for respiratory tract infections. It also has prokinetic effects on the GI tract, which can be utilized in gastroparesis but may cause abdominal cramping.
Biaxin (clarithromycin) is a macrolide antibiotic with activity against atypical pathogens (e.g., Legionella, Mycoplasma, Chlamydia). It is a potent CYP3A4 inhibitor, increasing levels of statins, warfarin, and colchicine. Use caution in myasthenia gravis; may exacerbate weakness. QT prolongation risk: avoid use with other QT-prolonging drugs, correct electrolyte abnormalities. For H. pylori eradication, combine with amoxicillin and a PPI as first-line. Renal dose adjustment required for Cr Cl <30 m L/min.
Take this medication exactly as prescribed, usually every 6 hours or as directed.,Complete the full course even if you feel better to prevent resistance.,May cause stomach upset; taking with food can reduce GI irritation.,Avoid grapefruit juice as it may affect drug levels.,Report symptoms of liver problems (yellowing skin/eyes, dark urine) or hearing loss immediately.,Do not take with certain medications like statins or warfarin without consulting your doctor.,Use effective contraception if applicable, as erythromycin may reduce birth control pill efficacy.
Take with or without food, but taking with food may reduce stomach upset.,Complete the full course even if you feel better to prevent resistance.,Avoid grapefruit or grapefruit juice while on this medication.,Report any signs of liver problems: yellowing of skin/eyes, dark urine, severe nausea/vomiting.,May cause metallic or bitter taste in the mouth; this is usually temporary.,Tell your doctor if you have myasthenia gravis, as clarithromycin can worsen symptoms.,Avoid driving or operating heavy machinery if you experience dizziness or vision changes.,Use effective contraception if applicable; clarithromycin may reduce oral contraceptive efficacy.
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 E.E.S. 400 vs BIAXIN, answered by our medical review team.
E.E.S. 400 is a Macrolide Antibiotic that works by Erythromycin, a macrolide antibiotic, binds to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis. At high concentrations, it may also inhibit RNA synthesis.. BIAXIN is a Macrolide Antibiotic that works by Binds to the 50S ribosomal subunit, inhibiting bacterial protein synthesis by blocking peptide chain elongation.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between E.E.S. 400 and BIAXIN depend on the specific clinical indication. These are both Macrolide Antibiotic agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of E.E.S. 400 is: Erythromycin ethylsuccinate 400 mg orally every 6 hours. For severe infections, up to 4 g/day in divided doses.. The standard adult dose of BIAXIN is: 250-500 mg orally every 12 hours for 7-14 days; extended-release: 1000 mg orally every 24 hours for 7-14 days. 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 E.E.S. 400 and BIAXIN 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. E.E.S. 400 is classified as Category C. FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; inadequate human studies in first trimester. No known risk of major birth defects or miscarriage. Avoid i. BIAXIN is classified as Category C. FDA Pregnancy Category C. Animal studies have shown fetal harm (cleft palate, skeletal abnormalities) at doses 2-5 times the human clinical dose. No adequate human studies. First t. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.