Recommended Dosage of Intravenous (IV) Imipenem/Cilastatin
The recommended dose of intravenous imipenem/cilastatin for most infections is 500 mg every 6 hours or 1000 mg every 8 hours for patients with normal renal function (creatinine clearance ≥90 mL/min). 1
Dosing Based on Infection Severity and Pathogen Susceptibility
The appropriate dosing regimen depends on the suspected or confirmed pathogen susceptibility:
For susceptible bacterial species:
- 500 mg every 6 hours OR
- 1000 mg every 8 hours 1
For bacterial species with intermediate susceptibility:
- 1000 mg every 6 hours 1
For severe infections like carbapenem-resistant Enterobacterales:
- 1.25 g IV every 6 hours is recommended for bloodstream infections, complicated UTIs, and complicated intra-abdominal infections 2
Administration Guidelines
- Doses ≤500 mg should be administered by IV infusion over 20-30 minutes
- Doses >500 mg should be administered by IV infusion over 40-60 minutes
- For patients who develop nausea during infusion, the rate may be slowed 1
Dosage Adjustment for Renal Impairment
Dosage must be reduced for patients with decreased renal function according to creatinine clearance:
| Creatinine Clearance (mL/min) | Dosage for Susceptible Pathogens |
|---|---|
| ≥90 | 500 mg q6h or 1000 mg q8h |
| <90 to ≥60 | 400 mg q6h or 500 mg q6h |
| <60 to ≥30 | 300 mg q6h or 500 mg q8h |
| <30 to ≥15 | 200 mg q6h or 500 mg q12h |
| <15 | Requires further dose reduction |
Important Clinical Considerations
- The maximum total daily dosage should not exceed 4 g/day 1
- Imipenem is metabolized by renal dehydropeptidase I, which is why it's always co-administered with cilastatin (in a 1:1 ratio) to inhibit this metabolism and increase urinary recovery of active imipenem 3
- Cilastatin is eliminated more slowly than imipenem in patients with renal impairment, necessitating dose adjustments 4
- For patients on hemodialysis, both imipenem and cilastatin are efficiently removed during a 4-hour session, requiring a supplementary dose after dialysis 4
Monitoring and Adverse Effects
- Routine monitoring should include complete blood count, renal function, and liver function tests throughout treatment 2
- Common adverse effects: nausea, vomiting, diarrhea, rash, thrombophlebitis, and eosinophilia
- Serious adverse effects: seizures, anaphylaxis, and C. difficile-associated diarrhea
- Concomitant use of valproate should be avoided due to reduced serum concentrations of valproate 2
Treatment Duration
Treatment duration depends on the type of infection:
- Bloodstream infections: 7-14 days
- Complicated UTIs and intra-abdominal infections: 5-7 days 2