(Redirected from Ampicillin-sulbactam)


  • Type: Amino-Penicillins
  • Dosage Forms: powder for solution
  • Dosage Strengths: 1.5g, 3g, 15g
  • Routes of Administration: IM, IV
  • Common Trade Names: Unasyn

Adult Dosing


  • 1.5-3g IV/IM q6 hours
  • Max: 12g/day

Bite (for Pasteurella multocida Coverage)

  • 1.5-3g IM/IV q6 hours

Orbital Cellulitis

  • 3g IM/IV q6 hours

Diabetic Foot Osteomyelitis[1]

  • 3g IM/IV q6 hours



  • Aspiration or CAP
    • 1.5-3g IM/IV q6 hours
  • Hospital-acquired: 3g IM/IV q6 hours

UTI, Pyelonephritis

  • 3g IM/IV q6 hours x 14 days

Pediatric Dosing (<40kg)

Unasyn (ampicillin/sulbactam) is formulated at a 2:1 ratio (3g vial = 2g ampicillin + 1g sulbactam)


  • Mild-moderate
    • 100-200mg ampicillin/kg/day IM/IV divided q6 hours
    • First Dose: 25-50mg ampicillin/kg IM/IV x 1 (37.5-75mg Unasyn/kg IM/IV x 1)
    • Max: 1000mg ampicillin (1500mg Unasyn)
  • Severe
    • 200mg ampicillin/kg/day IM/IV divided q6 hours
    • First Dose: 50mg ampicillin/kg IM/IV x 1 (75mg Unasyn/kg IM/IV x 1)
    • Max: 2000mg ampicillin (3000mg Unasyn)


  • 400mg ampicillin/kg/day IM/IV divided q6 hours
  • First Dose: 100mg ampicillin/kg IM/IV x 1 (150mg Unasyn/kg IM/IV x 1)
  • Max: 2000mg ampicillin (3000mg Unasyn)


  • 200mg ampicillin/kg/day IM/IV divided q4-6 hours +/- gentamicin x 4-6 weeks


  • 200mg ampicillin/kg/day IM/IV divided q6 hours

Special Populations

  • Pregnancy: B
  • Lactation: Use caution
  • Renal Dosing
    • Adult
    • Pediatric
  • Hepatic Dosing
    • Adult
    • Pediatric


  • Allergy to class/drug

Adverse Reactions


  • Anaphylaxis


  • Headache
  • Itching
  • Nausea
  • Vomiting


  • Half-life: One hour
  • Metabolism:
  • Excretion: Renal (75% excreted in active form), Bile (very small amount)[3]
  • Mechanism of Action: Bactericidal (Binds to penicillin-binding proteins to block cell wall synthesis), coupled with β-lacatamase inhibitor

Antibiotic Sensitivities[4]

Group Organism Sensitivity
Gram Positive Strep. Group A, B, C, G S
Strep. Pneumoniae S
Viridans strep I
Strep. anginosus gp S
Enterococcus faecalis S
Enterococcus faecium S
Staph. Epidermidis R
C. jeikeium R
L. monocytogenes S
Gram Negatives N. gonorrhoeae S
N. meningitidis S
Moraxella catarrhalis S
H. influenzae S
E. coli S
Klebsiella sp S
E. coli/Klebsiella ESBL+ R
E coli/Klebsiella KPC+ R
Enterobacter sp, AmpC neg R
Enterobacter sp, AmpC pos R
Serratia sp R
Serratia marcescens X1
Salmonella sp S
Shigella sp S
Proteus mirabilis S
Proteus vulgaris S
Providencia sp. S
Morganella sp. S
Citrobacter freundii R
Citrobacter diversus R
Citrobacter sp. R
Aeromonas sp S
Acinetobacter sp. S
Pseudomonas aeruginosa R
Burkholderia cepacia R
Stenotrophomonas maltophilia R
Yersinia enterocolitica I
Francisella tularensis X1
Brucella sp. X1
Legionella sp. R
Pasteurella multocida S
Haemophilus ducreyi S
Vibrio vulnificus X1
Misc Chlamydophila sp R
Mycoplasm pneumoniae R
Rickettsia sp X1
Mycobacterium avium X1
Anaerobes Actinomyces S
Bacteroides fragilis S
Prevotella melaninogenica S
Clostridium difficile X2
Clostridium (not difficile) S
Fusobacterium necrophorum S
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. Lipsky, 2004
  2. Red Book, 2012
  3. Campoli-Richards DM, Brogden RN. (1987). ". Sulbactam/ampicillin: a review of its antibacterial activity, pharmacokinetic properties, and therapeutic use". Drugs. 33 (6): 577–609. doi:10.2165/00003495-198733060-00003. PMID 3038500
  4. Sanford Guide to Antimicrobial Therapy 2014