Imipenem/Cilastatin (Primaxin)

Category:

• Antibiotic

Description:

• Carbapenem with dihydropeptidase inhibitor

  • 250mg cilastatin per 250mg of imipenem

Indications:

• Lower respiratory tract infections (S. aureus, E. coli, H. influenzae, H. parainfluenzae, Klebsiella species, Enterobacter species, Acetinobacter species, Serratia species)

• Urinary tract infections (Enterococcus faecalis, S. aureus, E. coli, Klebsiella species, Proteus vulgaris, Enterobacter species, Providencia rettgeri, Morganella morganii, Pseudomonas aeruginosa)

• Intra-abdominal infections (E. faecalis, S. aureus, E. coli, S. epidermidis, Streptococcus species, Enterobacter species, Klebsiella species, Bacteroides species, Proteus species, M. mogranii, P. aeruginosa, Citrobacter species, Peptococcus species, Peptostreptococcus species, Bacteroides species, Fusobacterium species, Eubacterium species, Propionibacterium species, Bifidobacterium species)

• Gynecological infections (E. faecalis, S. aureus, S. epidermidis, Streptococcus agalactiae, E. coli, Klebsiella species, Proteus species, Enterobacter species, Bifidobacterium species, Bacteroides species, Gardnerella vaginalis, , Peptococcus species, Peptostreptococcus species, Propionibacterium species)

• Bacterial septicemia (E. faecalis, S. aureus, E. coli, Klebsiella species, P. aeruginosa, Serratia species, Enterobacter species, Bacteroides species)

• Bone and joint infections (E. faecalis, S. aureus, S. epidermidis, Enterobacter species, P. aeruginosa)

• Skin infections (E. faecalis, S. aureus, S. epidermidis, E. coli, Klebsiella species, Enterobacter species, P. vulgaris, P. rettgeri, M. morganii, P. aeruginosa, Serratia species, Citrobacter species, Peptococcus species, Peptostreptococcus species, Acinetobacter species,  Fusobacterium species, Bacteroides species)

• Endocarditis (S. aureus)

• Polymicrobic infections (S. pneumoniae, S. pyogenes, S. aureus, P. aeruginosa)

Contraindications:

• Beta-lactam allergies  

Precautions:

• Pregnancy category C

• Use with caution in patients with PCN or cephalosporin allergy (5-10% chance of cross-reactivity)

• Use in caution with patients having CNS disorders (brain lesions, seizure history) due to increased risk of CNS side effects (see below).

• Use alternate form of birth control (disrupts absorption of oral contraceptives and renders them inactive)

• Dosage modifications are generally only required in patients with severe renal impairment

• IM injection dosages over 1500mg per day are not recommended  

Adverse Reactions (Side Effects):

• CNS: fever (0.5%), seizures (0.4%), dizziness, somnolence, tremor, confusion, headache, hallucinations

• Dermatological: rash, pruritis, urticaria

• Gastrointestinal: nausea (2%), diarrhea, vomiting

• Local pain at injection site

• Hearing loss, tinnitis, taste changes

• Pediatric patients: diarrhea (4%), phlebitis (2.2%)

• Newborns to 3 months: convulsions (6%), diarrhea (3%)

Dosage:

Administered by IM or IV injection over 40-60 minutes for >500mg/dose, over 15-30 minutes for <500mg/dose

• Adult (> 60kg):

  • mild infection: 250-500mg q6h (totally daily dose 2 grams)

  • moderate infections: 500mg q6-8h (total daily dose 2-3 grams)

  • severe infections: 500mg q6h (total daily dose 3-4 grams)

  • uncomplicated UTI: 250mg q6h (totally daily dose 1 gram)

  • complicated UTI: 500mg q6h (total daily dose 2 grams)

• Pediatric (>3 months):

  • 15-25mg/kg/dose q6h

• Pediatric (<3 months):

  • <1 week: 25mg/kg q12h

  • 1-4 weeks: 25mg/kg q8h

  • 1-3 months: 25mg q6h

• Child (< 60kg):

  • dosed at 50mg/kg/dose

  • mild to moderate infections: 200mg/kg/day every 6 hours

  • severe infections: 300mg/kg/day every 4 hours