Imipenem: Recommended Use and Dosage for Bacterial Infections
Imipenem is recommended for treating serious bacterial infections at a standard dosage of 500 mg every 6 hours or 1 gram every 8 hours intravenously for patients with normal renal function. 1
Indications for Use
Imipenem, a carbapenem antibiotic, is indicated for the treatment of:
- Complicated intra-abdominal infections (5-7 days treatment duration) 2
- Necrotizing infections of skin, fascia, and muscle (mixed infections) 2
- Complicated urinary tract infections (5-7 days treatment duration) 2
- Bloodstream infections (7-14 days treatment duration) 2
Dosage Recommendations
Adult Patients with Normal Renal Function (CrCl ≥90 mL/min):
- For susceptible bacterial species: 500 mg IV every 6 hours OR 1,000 mg IV every 8 hours 1
- For bacterial species with intermediate susceptibility: 1,000 mg IV every 6 hours 1
- Maximum daily dose: Should not exceed 4 g/day 1
Administration:
- Doses ≤500 mg: Administer by IV infusion over 20-30 minutes
- Doses >500 mg: Administer by IV infusion over 40-60 minutes
- For patients who develop nausea during infusion, the rate may be slowed 1
Pediatric Dosing:
- Children ≥3 months: 15-25 mg/kg every 6 hours
- Children 4 weeks to 3 months: 25 mg/kg every 6 hours
- Children 1-4 weeks: 25 mg/kg every 8 hours
- Children <1 week: 25 mg/kg every 12 hours 1
Dosage Adjustments for Renal Impairment
Renal dosage adjustment is critical to prevent toxicity:
| Creatinine Clearance (mL/min) | Dosage for Susceptible Bacteria |
|---|---|
| ≥90 | 500 mg q6h or 1,000 mg q8h |
| 60-89 | 400 mg q6h or 500 mg q6h |
| 30-59 | 300 mg q6h or 500 mg q8h |
| 15-29 | 200 mg q6h or 500 mg q12h |
| <15 | Not recommended unless on hemodialysis |
Caution: Patients with creatinine clearance <30 mL/min have increased risk of seizures 1
Clinical Considerations
Antimicrobial Spectrum
Imipenem has one of the broadest spectrums of antimicrobial activity among available antibiotics, covering:
- Gram-positive aerobes (including streptococci and methicillin-sensitive staphylococci)
- Gram-negative aerobes (including Pseudomonas)
- Anaerobes 3
Combination Therapy
- For mixed aerobic-anaerobic infections, imipenem can be used as monotherapy 2
- For serious Pseudomonas infections, consider combination with an aminoglycoside to prevent resistance development 4
Important Precautions
- Seizure risk: Higher in patients with CNS disorders or renal impairment 5
- Not recommended for pediatric patients with CNS infections due to seizure risk 1
- Resistance concerns: Stenotrophomonas maltophilia and some strains of Pseudomonas cepacia are typically resistant 4
Special Populations
Hemodialysis Patients
- Administer after hemodialysis session
- Use dosing for CrCl 15-29 mL/min
- Carefully monitor dialysis patients, especially those with CNS disease 1
Pitfalls and Caveats
- Seizure risk: Closely monitor patients with history of seizures, CNS disease, or renal impairment
- Resistance development: Can occur during treatment of Pseudomonas infections
- Dosing errors: Ensure proper dosage adjustment in renal impairment
- Administration rate: Infusion-related nausea and vomiting can be reduced by slowing infusion rate
Imipenem is administered with cilastatin, which inhibits renal metabolism of imipenem, increasing urinary concentrations and preventing nephrotoxicity 4.