Imipenem Dosing for Pseudomonas Infections
For Pseudomonas aeruginosa infections, imipenem should be dosed at 500 mg every 6 hours or 1 g every 8 hours for susceptible strains, and increased to 1 g every 6 hours for strains with intermediate susceptibility. 1, 2
Standard Dosing Recommendations
The dosing of imipenem for Pseudomonas infections depends on the susceptibility of the organism and the site of infection:
For Susceptible Pseudomonas aeruginosa:
- 500 mg IV every 6 hours OR
- 1 g IV every 8 hours 2
For Pseudomonas with Intermediate Susceptibility:
- 1 g IV every 6 hours 2
For Difficult-to-Treat Pseudomonas (DTR-PA):
- Imipenem/cilastatin/relebactam 1.25 g IV every 6 hours 1
Administration Guidelines
- Doses ≤500 mg should be infused over 20-30 minutes
- Doses >500 mg should be infused over 40-60 minutes
- In patients who develop nausea during infusion, the rate may be slowed 2
Dosage Adjustments for Renal Impairment
Renal function significantly impacts imipenem dosing:
| Creatinine Clearance (mL/min) | Susceptible Strains | Intermediate Susceptibility |
|---|---|---|
| ≥90 | 500 mg q6h or 1 g q8h | 1 g q6h |
| <90 to ≥60 | 400 mg q6h or 500 mg q6h | 750 mg q8h |
| <60 to ≥30 | 300 mg q6h or 500 mg q8h | 500 mg q6h |
| <30 to ≥15 | 200 mg q6h or 500 mg q12h | 500 mg q12h |
Important: Patients with creatinine clearance <30 mL/min have an increased risk of seizures. Imipenem is not recommended for patients with creatinine clearance <15 mL/min unless hemodialysis is instituted within 48 hours 2.
Treatment Duration
The duration of therapy should be tailored to the specific infection site:
- Complicated urinary tract infections: 5-10 days
- Complicated intra-abdominal infections: 5-10 days
- Hospital-acquired or ventilator-associated pneumonia: 10-14 days
- Bloodstream infections: 10-14 days 1
Special Considerations
Risk of Resistance
- Resistance to imipenem may emerge during treatment of P. aeruginosa infections 3, 4
- Monotherapy for Pseudomonas aeruginosa infections may lead to resistance development 5
- Consider combination therapy with an aminoglycoside for severe infections 6
Maximum Daily Dose
- The maximum total daily dosage should not exceed 4 g/day 2
Combination Therapy
For difficult-to-treat Pseudomonas aeruginosa (DTR-PA), consider:
- Combination therapy with an aminoglycoside (such as amikacin 15 mg/kg IV daily)
- Alternative options like ceftolozane/tazobactam or ceftazidime/avibactam 1, 6
Monitoring
- Monitor renal function regularly during treatment
- For patients on hemodialysis, administer imipenem after hemodialysis and time intervals from the end of the session 2
- Monitor for seizures, especially in patients with renal impairment or CNS disorders 2, 4
Pitfalls to Avoid
- Avoid monotherapy for severe Pseudomonas infections due to risk of resistance development 6, 5
- Do not exceed 4 g/day total dose regardless of infection severity 2
- Imipenem is not recommended in pediatric patients with CNS infections due to risk of seizures 2
- Do not use in patients with creatinine clearance <15 mL/min without hemodialysis 2
By following these evidence-based dosing recommendations, optimal therapeutic outcomes can be achieved while minimizing the risk of adverse effects and resistance development.