Imipenem/Cilastatin

General
  • Type: Carbapenems
  • Dosage Forms:
  • Common Trade Names: Primaxin

Adult Dosing

General
  • Fully-susceptible organisms: 500mg IV q6 hours
  • Moderately-susceptible organisms: 1g IV q6-8 hours
  • Max: Lower of 50mg/kg or 4 g/day

UTI
  • 500mg IV q6h

Pneumonia, hospital acquired
  • 500mg IV q6h x7 days

Anthrax, systemic
  • 1g IV q6h for at least 2wk

Pediatric Dosing

General[1]
  • 60-100mg/kg/day IV divided q6 hours
  • First Dose: 10-16.6mg/kg IV x 1
  • Max: 4000mg/day

Anthrax, systemic
  • Neonates >32 wk gestation
    • 40-75 mg/kg/day IV divided q8-12h for at least 2wk
  • 1 month and older
    • 100 mg/kg/day IV divided q6h for at least 2wk

Special Populations
  • Pregnancy: C
  • Lactation: Use caution
  • Renal Dosing
    • Adult
      • If usual dose 500mg q6h
        • CrCl 60-89: 400mg q6h
        • CrCl 30-59: 300mg q6h
        • CrCl 15-29: 200mg q6h
        • CrCl <15: Avoid unless HD w/in 48h
        • HD: 200mg q6h, give dose after dialysis, no supplement
        • PD: No supplement
      • If usual dose 1000mg q8h
        • CrCl 60-89: 500mg q6h
        • CrCl 30-59: 500mg q8h
        • CrCl 15-29: 500mg q12h
        • CrCl <15: Avoid unless HD w/in 48h
        • HD: 500mg q12h, give dose after dialysis, no supplement
        • PD: No supplement
      • If usual dose 1000mg q6h
        • CrCl 60-89: 750mg q8h
        • CrCl 30-59: 500mg q6h
        • CrCl 15-29: 500mg q12h
        • CrCl <15: Avoid unless HD w/in 48h
        • HD: 500mg q12h, give dose after dialysis, no supplement
        • PD: No supplement
    • Pediatric
      • < 30 kg: Avoid use in renal impairment
      • > 30 kg:
        • CrCl 41-70: Decrease dose 50%
        • CrCl 21-40: Decrease dose 63%; give q8h
        • CrCl 6-20: Decrease dose 75%, give q12h
        • CrCl <5: Avoid unless HD w/in 48h
        • HD: Give dose after dialysis, no supplement
        • PD: No supplement
  • Hepatic Dosing
    • Adult: Not defined
    • Pediatric: Not defined

Contraindications
  • Allergy to class/drug

Adverse Reactions

Serious

Common

Pharmacology
  • Half-life: 1h
  • Metabolism:
    • Imipenem: Kidney
    • Cilastatin: Unknown
  • Excretion: Urine 70%
  • Mechanism of Action:
    • Bactericidal
    • Imipenem inhibits cell wall synthesis
    • Cilastatin inhibits renal dihydropeptidase I, preventing imipenem metabolism

Antibiotic Sensitivities[2]
Group Organism Sensitivity
Gram PositiveStrep. Group A, B, C, GS
Strep. PneumoniaeS
Viridans strepS
Strep. anginosus gpS
Enterococcus faecalisS
Enterococcus faeciumI
MSSAS
MRSAR
CA-MRSAR
Staph. EpidermidisS
C. jeikeiumR
L. monocytogenesS
Gram NegativesN. gonorrhoeaeX2
N. meningitidisS
Moraxella catarrhalisS
H. influenzaeS
E. coliS
Klebsiella spS
E. coli/Klebsiella ESBL+S
E coli/Klebsiella KPC+R
Enterobacter sp, AmpC negS
Enterobacter sp, AmpC posS
Serratia spS
Serratia marcescensX1
Salmonella spS
Shigella spS
Proteus mirabilisS
Proteus vulgarisS
Providencia sp.S
Morganella sp.S
Citrobacter freundiiS
Citrobacter diversusS
Citrobacter sp.S
Aeromonas spS
Acinetobacter sp.I
Pseudomonas aeruginosaS
Burkholderia cepaciaR
Stenotrophomonas maltophiliaR
Yersinia enterocoliticaS
Francisella tularensisX1
Brucella sp.X1
Legionella sp.R
Pasteurella multocidaS
Haemophilus ducreyiX1
Vibrio vulnificusX1
MiscChlamydophila spR
Mycoplasm pneumoniaeR
Rickettsia spX1
Mycobacterium aviumX1
AnaerobesActinomycesS
Bacteroides fragilisS
Prevotella melaninogenicaS
Clostridium difficileX2
Clostridium (not difficile)S
Fusobacterium necrophorumS
Peptostreptococcus sp.S

Key
  • 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

References
  1. Red Book, 2012
  2. Sanford Guide to Antimicrobial Therapy 2014
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