Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
Ampicillin vs AMCILL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Ampicillin is a penicillin antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity, and disrupting peptidoglycan cross-linking.
Ampicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death.
Respiratory tract infections,Urinary tract infections,Meningitis,Septicemia,Endocarditis,Gastrointestinal infections,Intra-abdominal infections,Skin and soft tissue infections,Prophylaxis for bacterial endocarditis (off-label),Listeriosis
Infections of the respiratory tract,Infections of the genitourinary tract,Meningitis,Septicemia,Endocarditis,Gastrointestinal infections,Prophylaxis of bacterial endocarditis
250-500 mg orally every 6 hours; 1-2 g IV/IM every 4-6 hours.
250-500 mg orally every 8 hours or 500 mg every 12 hours; for severe infections, up to 1 g every 6 hours intravenously.
Terminal elimination half-life: 1-1.8 hours in adults with normal renal function; prolonged to 7-20 hours in end-stage renal disease (Cr Cl <10 m L/min).
1-1.5 hours in normal renal function; prolonged to 7-10 hours in anuria.
Ampicillin is primarily excreted unchanged in the urine via renal tubular secretion and glomerular filtration. A small portion is metabolized by hydrolysis to penicilloic acid, but hepatic metabolism is minimal.
Partially metabolized by hydrolysis; primarily excreted unchanged in urine via renal tubular secretion and glomerular filtration.
Renal: 90% unchanged via glomerular filtration and tubular secretion; biliary: 10% (small amount).
Renal: 60-80% unchanged; biliary: less than 10%; fecal: small amount.
17-20% bound to serum albumin.
20% bound, primarily to albumin.
0.28-0.31 L/kg (higher in neonates and critically ill patients).
0.3 L/kg; indicates distribution into extracellular fluid.
Oral: 50% (fasting); reduced by 25-50% with food. IM: ~100% (complete absorption).
Oral: 50-70% (variable, reduced by food); IM: nearly 100%.
Cr Cl 10-50 m L/min: administer every 6-12 hours; Cr Cl <10 m L/min: administer every 12-24 hours.
For Cr Cl 30-50 m L/min: administer every 12 hours; for Cr Cl 10-29 m L/min: administer every 18-24 hours; for Cr Cl <10 m L/min: administer every 24 hours.
No adjustment needed for hepatic impairment; dose as in normal hepatic function.
No specific adjustments recommended for Child-Pugh A or B; use caution in severe hepatic impairment (Child-Pugh C) with monitoring.
Neonates: 25-50 mg/kg IV/IM every 12 hours (first week), every 8 hours (1-4 weeks); Infants/Children: 25-100 mg/kg/day IV/IM divided every 6-8 hours; Oral: 50-100 mg/kg/day divided every 6-8 hours.
Children >1 month: 25-50 mg/kg/day orally divided every 8 hours; for severe infections, up to 100 mg/kg/day IV divided every 6 hours. Maximum dose: 2 g/day.
Cr Cl >50 m L/min: no adjustment; Cr Cl 10-50 m L/min: administer every 6-12 hours; Cr Cl <10 m L/min: administer every 12-24 hours; maximum 2 g/day.
No specific dose adjustment required; monitor renal function and adjust based on creatinine clearance.
Serious and occasionally fatal hypersensitivity reactions (anaphylaxis) have been reported in patients on penicillin therapy. Clostridium difficile-associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents.
No FDA black box warning.
Serious hypersensitivity reactions (anaphylaxis) requiring emergency treatment,Clostridium difficile-associated diarrhea (CDAD) may occur,Prolonged use may result in superinfection with non-susceptible organisms,Use with caution in patients with renal impairment (dose adjustment needed),Skin rash is common in patients with mononucleosis or concurrent allopurinol use
Hypersensitivity reactions including anaphylaxis,Clostridioides difficile-associated diarrhea,Superinfection,Risk of seizures with high doses or renal impairment,Use caution in patients with mononucleosis (high risk of rash)
Hypersensitivity to ampicillin or any penicillin,Hypersensitivity to cephalosporins (cross-allergenicity possible),Infections caused by penicillinase-producing bacteria (including methicillin-resistant Staphylococci)
Hypersensitivity to ampicillin, penicillins, or any component of the formulation,Infections caused by beta-lactamase-producing organisms
Food decreases absorption of oral ampicillin; take on an empty stomach. No specific food restrictions aside from timing. Avoid alcohol as it may increase gastrointestinal irritation.
Food does not significantly affect absorption; may be taken with or without meals. Avoid alcohol: may increase risk of disulfiram-like reaction (rare).
Ampicillin is FDA Pregnancy Category B. Animal studies have not demonstrated teratogenic effects. In humans, ample data across all trimesters indicate no increased risk of major birth defects, though there is a theoretical risk of altered gut flora and maternal-fetal effects from high doses. No documented teratogenicity from controlled studies in pregnant women.
FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. First trimester: Not associated with major birth defects. Second and third trimesters: Use only if clearly needed; potential for altered gut flora and diarrhea in neonate.
Ampicillin is excreted in breast milk in low concentrations. The milk-to-plasma (M/P) ratio is approximately 0.2–0.3. Amount ingested by the infant is estimated to be <0.1% of a therapeutic neonatal dose. The American Academy of Pediatrics considers it compatible with breastfeeding. Monitor infant for potential diarrhea, rash, or candidiasis.
Ampicillin is excreted in breast milk in low concentrations (M/P ratio approximately 0.2). Compatible with breastfeeding; monitor infant for diarrhea or rash.
Pregnancy increases renal clearance and volume of distribution for ampicillin, potentially lowering serum concentrations. For standard infections, no dose adjustment is routinely needed. However, for serious infections (e.g., meningitis, endocarditis), higher doses or more frequent intervals may be required to achieve therapeutic levels. Consider therapeutic drug monitoring in severe cases.
Increased renal clearance during pregnancy may require higher doses to maintain therapeutic levels. Standard dosing is usually adequate for most indications; consider monitoring serum levels in severe infections.
Ampicillin is a bactericidal antibiotic that inhibits cell wall synthesis. It is effective against Gram-positive cocci (except penicillinase-producing staphylococci) and some Gram-negative bacilli. Use with probenecid to increase serum levels. Monitor for rash, which may indicate mononucleosis. Dose adjustment required in renal impairment (Cr Cl <30 m L/min). Administer IV slowly over 10-15 minutes to avoid phlebitis.
AMCILL (ampicillin) is a broad-spectrum penicillinase-sensitive penicillin. Use caution in patients with renal impairment; dose adjustment required for Cr Cl <30 m L/min. Monitor for hypersensitivity reactions, especially in patients with cephalosporin allergy. IV administration may cause phlebitis; rotate infusion sites. Not effective against penicillinase-producing organisms including Staphylococcus aureus.
Take ampicillin exactly as prescribed, even if you feel better.,Complete the full course of therapy to prevent resistance.,Take on an empty stomach (1 hour before or 2 hours after meals) for best absorption.,Oral suspension must be refrigerated; shake well before each use.,Discard any unused oral suspension after 14 days.,Report any skin rash, diarrhea, or difficulty breathing to your doctor immediately.,Do not use if you are allergic to penicillins or cephalosporins.,Avoid alcohol while on this medication to reduce risk of side effects.,May reduce the effectiveness of oral contraceptives; use additional birth control.
Take exactly as prescribed; complete full course even if you feel better.,Notify your doctor if you develop rash, hives, or difficulty breathing.,May cause diarrhea; contact your doctor if severe or bloody.,Take with a full glass of water; avoid acidic beverages like orange juice.,Inform your doctor if you are pregnant, breastfeeding, or taking oral contraceptives (ampicillin may reduce efficacy).
"The coadministration of ampicillin, a broad-spectrum penicillin antibiotic, with streptozocin, a nitrosourea antineoplastic agent used in pancreatic islet cell carcinoma, may reduce serum concentrations of streptozocin. This interaction is hypothesized to result from ampicillin-induced alterations in gut microbiota, leading to reduced enterohepatic recirculation of streptozocin metabolites or interference with renal tubular secretion of the active drug. Clinically, this could diminish the anticancer efficacy of streptozocin, potentially compromising tumor response."
"Ampicillin may reduce the serum concentration of Kanamycin via direct chemical inactivation in body fluids, particularly in patients with renal impairment. This interaction can lead to subtherapeutic aminoglycoside levels, potentially compromising antibacterial efficacy and promoting bacterial resistance. Clinically, this necessitates careful monitoring of Kanamycin levels and dose adjustments to maintain therapeutic effect."
"Ampicillin, a beta-lactam antibiotic, can reduce the serum concentration of plicamycin, an antineoplastic antibiotic, when co-administered. This interaction likely occurs due to ampicillin-induced alterations in gut microbiota, which may decrease the enterohepatic recirculation of plicamycin, leading to reduced systemic exposure. The resulting subtherapeutic plicamycin levels may compromise its antitumor efficacy and increase the risk of treatment failure."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about Ampicillin vs AMCILL, answered by our medical review team.
Ampicillin is a Penicillin Antibiotic that works by Ampicillin is a penicillin antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity, and disrupting peptidoglycan cross-linking.. AMCILL is a Penicillin Antibiotic that works by Ampicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between Ampicillin and AMCILL 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 Ampicillin is: 250-500 mg orally every 6 hours; 1-2 g IV/IM every 4-6 hours.. The standard adult dose of AMCILL is: 250-500 mg orally every 8 hours or 500 mg every 12 hours; for severe infections, up to 1 g every 6 hours intravenously.. 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 Ampicillin and AMCILL 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. Ampicillin is classified as Category A/B. Ampicillin is FDA Pregnancy Category B. Animal studies have not demonstrated teratogenic effects. In humans, ample data across all trimesters indicate no increased risk of major bi. AMCILL is classified as Category C. FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. First trimester: Not associated with major birth defects. Second and third trimesters: Use only if clearl. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.