Ampicillin is an antibiotic in the beta-lactam family of antibiotics. It is a Penicillin derivative.

  • Type: Penicillin
  • Dosage Forms: capsule, oral suspension, powder for injection
  • Dosage Strengths: capsule: 250, 500mg; oral suspension: 125, 250mg/5mL; powder for injection: 125mg, 250mg, 500mg, 1g, 2g, 10g
  • Routes of Administration: PO, IV, IM
  • Common Trade Names: Ampi, Omnipen, Penglobe, Principen

Pediatric Dosing

Pneumonia (peds)

  • 150-200mg/kg/day IV divided Q6hours (max dose: 4g per day)

Other Pediatric Bacterial Infections

  • 100-400mg/kg/day IM/IV divided q4-16Hours (max dose 12g/day IM/IV)

Special Populations

  • Pregnancy Rating: B
  • Lactation: Excreted in breastmilk, use caution
  • Renal dosing:
    • CrCl <10 mL/min: Administer q12-24hr
    • CrCl 10-50 mL/min: Administer q6-12hr
    • CrCl >50 mL/min: Administer q6hr
  • Hepatic Dosing: not studied


  • Allergy to class/drug

Adverse Reactions


  • Pseudomembranous colitis, enterocolitis
  • Agranulocytosis
  • Seizure
  • Interstitial nephritis
  • Stridor
  • Anaphylaxis


  • Rash, urticaria
  • Diarrhea, nausea
  • Fever
  • Oral candidiasis
  • Stomatitis, glossitis
  • Anemia/hemolytic anemia, leukopenia, thrombocytopenia, eosinophilia
  • Serum sickness like reaction
  • Elevated AST
  • Erythema multiforme


  • Half-life: 1-1.8 hr (normal renal function); 7-20 hr (anuria/ESRD)
  • Metabolism: Hepatic
  • Excretion: Urine
  • Mechanism of Action: Bactericidal; inhibits bacterial cell wall synthesis

Antibiotic Sensitivities[1]

Group Organism Sensitivity
Gram PositiveStrep. Group A, B, C, GS
Strep. PneumoniaeS
Viridans strepI
Strep. anginosus gpS
Enterococcus faecalisS
Enterococcus faeciumI
Staph. EpidermidisR
C. jeikeiumR
L. monocytogenesS
Gram NegativesN. gonorrhoeaeR
N. meningitidisS
Moraxella catarrhalisR
H. influenzaeI
E. coliI
Klebsiella spR
E. coli/Klebsiella ESBL+R
E coli/Klebsiella KPC+R
Enterobacter sp, AmpC negR
Enterobacter sp, AmpC posR
Serratia spR
Serratia marcescensX1
Salmonella spI
Shigella spI
Proteus mirabilisS
Proteus vulgarisR
Providencia sp.R
Morganella sp.R
Citrobacter freundiiR
Citrobacter diversusR
Citrobacter sp.R
Aeromonas spR
Acinetobacter sp.R
Pseudomonas aeruginosaR
Burkholderia cepaciaR
Stenotrophomonas maltophiliaR
Yersinia enterocoliticaR
Francisella tularensisX1
Brucella sp.X1
Legionella sp.R
Pasteurella multocidaS
Haemophilus ducreyiR
Vibrio vulnificusX1
MiscChlamydophila spR
Mycoplasm pneumoniaeR
Rickettsia spX1
Mycobacterium aviumX1
Bacteroides fragilisR
Prevotella melaninogenicaS
Clostridium difficileX1
Clostridium (not difficile)S
Fusobacterium necrophorumS
Peptostreptococcus sp.S


  • S susceptible/sensitive (usually)
  • I intermediate (variably susceptible/resistant)
  • R resistant (or not effective clinically)
  • S+ synergistic with cell wall antibiotics
  • U sensitive for UTI only (non systemic infection)
  • X1 no data
  • X2 active in vitro, but not used clinically
  • X3 active in vitro, but not clinically effective for Group A strep pharyngitis or infections due to E. faecalis
  • X4 active in vitro, but not clinically effective for strep pneumonia

See Also


  1. Sanford Guide to Antimicrobial Therapy 2014
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