Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
AMOXICILLIN vs AMOXIL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Amoxicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity, and activating autolytic enzymes.
Amoxicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation and activating autolytic enzymes, leading to bacterial lysis.
Upper respiratory tract infections (e.g., otitis media, sinusitis, pharyngitis/tonsillitis),Lower respiratory tract infections (e.g., community-acquired pneumonia, acute exacerbation of chronic bronchitis),Genitourinary tract infections (e.g., cystitis, urethritis),Skin and skin structure infections,Helicobacter pylori eradication (in combination with clarithromycin and a proton pump inhibitor),Lyme disease (early localized),Prophylaxis of infective endocarditis (for dental procedures in high-risk patients),Off-label: Anthrax (post-exposure prophylaxis), uncomplicated gonorrhea
Upper respiratory tract infections (e.g., otitis media, sinusitis, pharyngitis/tonsillitis) due to susceptible streptococci, pneumococci, and H. influenzae,Lower respiratory tract infections (e.g., pneumonia, bronchitis) due to susceptible streptococci, pneumococci, and H. influenzae,Genitourinary tract infections (e.g., uncomplicated gonorrhea, cystitis) due to susceptible E. coli, P. mirabilis, and enterococci,Skin and skin structure infections due to susceptible streptococci, staphylococci, and E. coli,Helicobacter pylori eradication (as part of combination therapy),Lyme disease (early localized or early disseminated),Prophylaxis of infective endocarditis (dental procedures) in patients with certain cardiac conditions
250-500 mg orally every 8 hours or 500-875 mg orally every 12 hours; for severe infections, up to 1 g orally every 8 hours.
250-500 mg orally every 8 hours or 500-875 mg orally every 12 hours; for severe infections, up to 500 mg every 8 hours or 875 mg every 12 hours.
Terminal elimination half-life: 1-1.5 hours in normal renal function. Prolonged to 7-20 hours in end-stage renal disease.
Terminal half-life: 1-1.5 hours (normal renal function); prolonged to 7-20 hours in anuria; neonates: 3-4 hours.
Amoxicillin is primarily metabolized by hydrolysis to penicilloic acid (inactive). It is not extensively metabolized by the liver; about 60% of an oral dose is excreted unchanged in urine.
Amoxicillin is primarily metabolized through hydrolysis of the beta-lactam ring to inactive penicilloic acid, accounting for 60-70% of the dose; about 10% is metabolized via hepatic pathways to amoxicilloic acid; renal excretion as unchanged drug is 60-80% via tubular secretion and glomerular filtration.
Renal: 60-80% unchanged via glomerular filtration and tubular secretion. Biliary: up to 20% excreted in bile. Fecal: minimal.
Renal: 60-80% unchanged via tubular secretion and glomerular filtration; Biliary/fecal: minor, <5% excreted in bile; dose adjustment in Cr Cl <30 m L/min.
17-20% bound to serum albumin.
17-20%, primarily to albumin.
0.3-0.4 L/kg. Distributes well into most body fluids and tissues, including pleural, peritoneal, and synovial fluids; limited CNS penetration unless meninges inflamed.
0.3-0.4 L/kg; indicates distribution into total body water.
Oral: 74-92% (absorption is not food-dependent). IM: approximately 100%.
Oral: 75-90% (variable with food, decreased absorption); IM: near 100%.
Cr Cl 30-50 m L/min: 250-500 mg every 8-12 hours. Cr Cl 10-29 m L/min: 250-500 mg every 12 hours. Cr Cl <10 m L/min: 250-500 mg every 24 hours. Hemodialysis: 250-500 mg every 24 hours, supplemented during and after dialysis.
GFR 10-30 m L/min: 250-500 mg every 12 hours; GFR <10 m L/min: 250-500 mg every 24 hours; hemodialysis: 250-500 mg every 24 hours with an additional dose after dialysis.
No dose adjustment required for mild to moderate hepatic impairment. Severe hepatic impairment (Child-Pugh class C): use with caution; specific dosing guidelines not established.
No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh class A or B); caution in severe hepatic impairment (Child-Pugh class C) due to limited data.
Children >3 months: 20-40 mg/kg/day divided every 8 hours for mild to moderate infections; 40-90 mg/kg/day divided every 8-12 hours for severe infections. Maximum 3 g/day.
Neonates ≤28 days: 25-30 mg/kg/day divided every 12 hours; Infants and children >28 days: 20-40 mg/kg/day divided every 8 hours; for otitis media: 50-90 mg/kg/day divided every 8-12 hours.
No specific dose adjustment; monitor renal function and adjust based on Cr Cl. Caution with concurrent nephrotoxic agents.
No specific dose adjustment based solely on age; monitor renal function and adjust dose based on creatinine clearance (Cr Cl) as per renal adjustment guidelines; maintain adequate hydration.
No FDA black box warning.
None
Hypersensitivity reactions including anaphylaxis have been reported; contraindicated in patients with known penicillin allergy.,Clostridium difficile-associated diarrhea (CDAD) may occur and must be considered in patients presenting with diarrhea after antibiotic use.,Serious skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis) can occur; discontinue if rash or other allergic signs appear.,Use caution in patients with renal impairment; dosage adjustment may be necessary.,Prolonged use may result in superinfection with non-susceptible organisms.
Serious hypersensitivity reactions (anaphylaxis) can occur; contraindicated in patients with penicillin allergy,Clostridium difficile-associated diarrhea (CDAD) may occur, ranging from mild diarrhea to fatal colitis,Prolonged use may result in superinfection with resistant organisms,Hepatic dysfunction and cholestatic jaundice (rare),Skin rashes, including morbilliform rash (common in patients with mononucleosis),Decreased efficacy when used with bacteriostatic agents (e.g., tetracyclines, chloramphenicol),Use with caution in patients with renal impairment (Cr Cl <30 m L/min) due to increased risk of seizures with high doses
History of hypersensitivity reaction to any penicillin or beta-lactam antibiotic.,Infectious mononucleosis (increases risk of maculopapular rash).,Phenylketonuria (some formulations contain aspartame).
Known hypersensitivity to amoxicillin, penicillins, or any component of the formulation,Mononucleosis (high incidence of morbilliform rash)
No significant food interactions. Absorption is not affected by food; may be taken with meals to reduce gastrointestinal upset. Avoid concurrent alcohol consumption as it may increase risk of side effects like nausea and vomiting.
No significant food interactions; absorption is not altered by food. Avoid excessive alcohol as it may increase risk of GI side effects and hepatotoxicity (rare).
FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. First trimester: no increased risk of major malformations observed in large cohort studies. Second and third trimesters: use only if clearly needed; no known fetal harm, but caution due to maternal physiological changes.
Penicillins, including amoxicillin, are generally considered low risk in pregnancy. Animal studies have not shown teratogenic effects. In humans, data from large cohort studies and meta-analyses do not indicate an increased risk of major congenital malformations, preterm birth, or low birth weight. Use is acceptable if clinically indicated across all trimesters.
Amoxicillin is excreted into breast milk in small amounts (M/P ratio approximately 0.014-0.015). Considered compatible with breastfeeding; potential for diarrhea or allergic sensitization in infant, but generally safe.
Amoxicillin is excreted into breast milk in small amounts, with an M/P ratio of approximately 0.02-0.05. The estimated dose to the infant is less than 1% of the maternal weight-adjusted dose. It is generally considered compatible with breastfeeding. However, potential risks include infant sensitization, diarrhea, and rash. Monitor for these effects.
No dose adjustment required for amoxicillin in pregnancy; however, increased renal clearance and expanded plasma volume may lower serum concentrations. For severe infections, consider standard dosing with monitoring of clinical response.
Physiologic changes in pregnancy (e.g., increased renal blood flow, GFR, and volume of distribution) may reduce serum concentrations of amoxicillin. While standard dosing may be effective, some experts recommend using the higher end of the dosing range or more frequent dosing for severe infections. However, no specific dose adjustment is routinely required; clinical response should guide therapy.
For streptococcal pharyngitis, amoxicillin 50 mg/kg once daily (max 1 g) is as effective as multiple daily doses and improves adherence. In penicillin-allergic patients, the cross-reactivity risk with cephalosporins is low; a cephalosporin can be used if no history of immediate-type hypersensitivity. Amoxicillin is not effective against penicillinase-producing staphylococci or most Gram-negative organisms due to beta-lactamase production. Monitor for rash in patients with infectious mononucleosis (ampicillin rash occurs more frequently, but amoxicillin also has increased risk). Dose adjustment needed for creatinine clearance <30 m L/min.
Amoxicillin is a first-line agent for acute otitis media, streptococcal pharyngitis, and uncomplicated community-acquired pneumonia. It has a time-dependent killing mechanism; optimal efficacy requires maintaining serum concentrations above the MIC for >40% of the dosing interval. Dose adjustment is necessary for creatinine clearance <30 m L/min. It is compatible with clavulanate for beta-lactamase coverage. Rash during therapy may indicate non-allergic ampicillin rash (especially with viral infections) or true hypersensitivity; assess carefully.
Take exactly as prescribed; complete the full course even if you feel better.,Can be taken with or without food; if stomach upset occurs, take with a meal.,Swallow capsules whole; do not crush or chew; oral suspension shake well before each dose.,Skip missed dose if almost time for next; do not double dose.,Seek immediate medical help for signs of allergic reaction: hives, difficulty breathing, swelling of face/lips/tongue.,May cause diarrhea; contact doctor if watery or bloody stools.,Inform doctor if you are pregnant, planning to become pregnant, or breastfeeding.,Avoid large amounts of grapefruit juice as it may affect absorption (limited clinical significance).
Take exactly as prescribed; complete the full course even if you feel better.,May be taken with or without food; avoid large meals if GI upset occurs.,Report any rash, especially if accompanied by hives or difficulty breathing.,Do not use leftover antibiotics; discard after completing course.,Use additional contraception if on oral contraceptives (may reduce efficacy).,For suspension: shake well, measure dose with provided device, refrigerate and discard after 14 days.
"Amoxicillin may reduce the metabolism of Indinavir via inhibition of CYP3A4, leading to increased plasma concentrations of Indinavir. This can elevate the risk of Indinavir-related toxicities such as nephrolithiasis, hepatotoxicity, and gastrointestinal intolerance. Patients may experience exacerbated adverse effects without a corresponding increase in antiviral efficacy."
"Amoxicillin may inhibit the CYP3A4-mediated metabolism of nicardipine, a calcium channel blocker, leading to increased plasma concentrations of nicardipine. This can potentiate vasodilation and negative chronotropic effects, resulting in an increased risk of hypotension, bradycardia, and peripheral edema. Patients, especially those with pre-existing cardiovascular conditions, should be monitored for enhanced antihypertensive effects and adverse reactions when these drugs are coadministered."
"Amoxicillin may inhibit the metabolism of bortezomib through competitive inhibition of cytochrome P450 enzymes, particularly CYP3A4 and CYP2C19, potentially leading to increased bortezomib exposure. This interaction could result in enhanced toxicity of bortezomib, including peripheral neuropathy, myelosuppression, and gastrointestinal adverse effects. Clinicians should monitor for signs of bortezomib toxicity when amoxicillin is coadministered, especially in patients with pre-existing hepatic impairment or other risk factors."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about AMOXICILLIN vs AMOXIL, answered by our medical review team.
AMOXICILLIN is a Penicillin Antibiotic that works by Amoxicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity, and activating autolytic enzymes.. AMOXIL is a Penicillin Antibiotic that works by Amoxicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation and activating autolytic enzymes, leading to bacterial lysis.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between AMOXICILLIN and AMOXIL depend on the specific clinical indication. These are both Penicillin 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 AMOXICILLIN is: 250-500 mg orally every 8 hours or 500-875 mg orally every 12 hours; for severe infections, up to 1 g orally every 8 hours.. The standard adult dose of AMOXIL is: 250-500 mg orally every 8 hours or 500-875 mg orally every 12 hours; for severe infections, up to 500 mg every 8 hours or 875 mg every 12 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 AMOXICILLIN and AMOXIL 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. AMOXICILLIN is classified as Category A/B. FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. First trimester: no increased risk of major malformations observed in large cohort studies. Second and th. AMOXIL is classified as Category C. Penicillins, including amoxicillin, are generally considered low risk in pregnancy. Animal studies have not shown teratogenic effects. In humans, data from large cohort studies and. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.