Intramuscular Administration of Ertapenem (Invanz)
Yes, ertapenem (Invanz) can be administered intramuscularly (IM) as an alternative to intravenous administration in appropriate clinical situations. The FDA-approved labeling specifically supports IM administration for up to 7 days of treatment 1.
Administration Routes and Bioavailability
- Intramuscular (IM): FDA-approved for up to 7 days of treatment
- Intravenous (IV): FDA-approved for up to 14 days of treatment
- Bioavailability: IM administration has 92% bioavailability compared to IV administration 2
Dosing for IM Administration
- Adults and pediatric patients ≥13 years: 1 gram once daily
- Pediatric patients 3 months to 12 years: 15 mg/kg twice daily (not to exceed 1 g/day)
- Renal impairment (adults): 500 mg daily if creatinine clearance ≤30 mL/min/1.73 m²
Clinical Scenarios Where IM Ertapenem Is Appropriate
IM ertapenem is particularly valuable in the following situations:
- Limited vascular access: When IV access is difficult to establish or maintain
- Outpatient management: For patients who don't require hospitalization but need parenteral therapy
- Transition from IV to IM: To facilitate earlier hospital discharge
- Emergency situations: When immediate antimicrobial therapy is needed but IV access is delayed
Specific Indications for IM Ertapenem
The FDA has approved IM ertapenem for the following infections 1:
- Complicated intra-abdominal infections
- Complicated skin and skin structure infections (including diabetic foot without osteomyelitis)
- Community-acquired pneumonia
- Complicated urinary tract infections including pyelonephritis
- Acute pelvic infections
Practical Considerations for IM Administration
- Pain management: IM injection may cause discomfort; consider local anesthetic
- Injection site: Use large muscle mass (gluteal or lateral thigh)
- Volume: The reconstituted solution should be used within 1 hour
- Contraindications: Avoid in patients with bleeding disorders or on anticoagulants
Special Situations
Sepsis Management
In sepsis or septic shock, when vascular access is limited, IM ertapenem can be used as part of the initial antimicrobial therapy to avoid delays in administration. The Surviving Sepsis Campaign guidelines specifically mention that "intramuscular preparations are approved and available for several first-line β-lactams, including... ertapenem" 3.
Alternative to Ceftriaxone
For gonorrhea treatment failures, ertapenem 1 g IM has been shown to be non-inferior to ceftriaxone for anogenital gonorrhea 3.
Necrotizing Fasciitis
For mixed infections in necrotizing fasciitis, ertapenem 1 g once daily is listed as a treatment option 3.
Limitations and Caveats
- Limited to 7 days of treatment via IM route (vs. 14 days for IV)
- Not suitable for Pseudomonas aeruginosa infections
- May not achieve adequate tissue concentrations as rapidly as IV administration in critically ill patients
IM ertapenem provides a valuable alternative to IV administration when appropriate, offering similar efficacy with the convenience of once-daily dosing and the potential to facilitate outpatient parenteral antimicrobial therapy.