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

• 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

• Hypersensitivity reaction
• Anaphylaxis
• Stevens-Johnson syndrome/Toxic epidermal necrolysis
• Erythema multiforme
• Neurotoxicity
• Seizure
• Superinfection
• C. diff associated diarrhea
• Hemorrhagic colitis
• Myelosuppression
• Hemolytic anemia
• Hepatotoxicity
• Acute renal failure

Common

• LFT Increase
• Seizure
• Platelet abnormality
• Diarrhea
• Thrombophlebitis
• Oliguria/Anuria
• Rash
• Nausea

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

Group	Organism	Sensitivity
Gram Positive	Strep. Group A, B, C, G	S
	Strep. Pneumoniae	S
	Viridans strep	S
	Strep. anginosus gp	S
	Enterococcus faecalis	S
	Enterococcus faecium	I
	MSSA	S
	MRSA	R
	CA-MRSA	R
	Staph. Epidermidis	S
	C. jeikeium	R
	L. monocytogenes	S
Gram Negatives	N. gonorrhoeae	X2
	N. meningitidis	S
	Moraxella catarrhalis	S
	H. influenzae	S
	E. coli	S
	Klebsiella sp	S
	E. coli/Klebsiella ESBL+	S
	E coli/Klebsiella KPC+	R
	Enterobacter sp, AmpC neg	S
	Enterobacter sp, AmpC pos	S
	Serratia sp	S
	Serratia marcescens	X1
	Salmonella sp	S
	Shigella sp	S
	Proteus mirabilis	S
	Proteus vulgaris	S
	Providencia sp.	S
	Morganella sp.	S
	Citrobacter freundii	S
	Citrobacter diversus	S
	Citrobacter sp.	S
	Aeromonas sp	S
	Acinetobacter sp.	I
	Pseudomonas aeruginosa	S
	Burkholderia cepacia	R
	Stenotrophomonas maltophilia	R
	Yersinia enterocolitica	S
	Francisella tularensis	X1
	Brucella sp.	X1
	Legionella sp.	R
	Pasteurella multocida	S
	Haemophilus ducreyi	X1
	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

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

• Antibiotics (Main)