What it's for (Indications)
- Imipenem/cilastatin (e.
- g.
- , Onem) is a broad-spectrum carbapenem antibiotic indicated for the treatment of serious bacterial infections caused by susceptible microorganisms.
- Its therapeutic applications encompass a wide array of conditions, including but not limited to, lower respiratory tract infections such as pneumonia and bronchitis, urinary tract infections (complicated and uncomplicated), intra-abdominal infections including appendicitis and peritonitis, gynecological infections such as endometritis, bacterial septicemia (bloodstream infections), bone and joint infections, skin and skin structure infections, and endocarditis.
- It is often reserved for infections caused by multi-drug resistant organisms or for empiric therapy in critically ill patients where a broad spectrum of activity, including against anaerobes, is required.
- The cilastatin component prevents the renal metabolism of imipenem, thereby enhancing its efficacy and reducing potential nephrotoxicity.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | The dosage of imipenem/cilastatin (e.g., Onem) must be individualized based on the type and severity of the infection, the susceptibility of the causative pathogen, the patient's renal function, and body weight, particularly in pediatric populations. For adults with normal renal function (creatinine clearance ≥ 70 mL/min/1.73 m²), typical intravenous dosages range from 250 mg to 1 gram of imipenem (co-administered with an equal amount of cilastatin) administered every 6 to 8 hours. The total daily dose generally should not exceed 4 grams. In patients with compromised renal function (creatinine clearance < 70 mL/min/1.73 m²), significant dosage adjustments are mandatory to prevent drug accumulation and mitigate the risk of central nervous system toxicity, including seizures. Pediatric dosing is based on weight and age, typically 15 to 25 mg/kg every 6 hours, not exceeding 2 grams daily. Each dose should be infused slowly over 20 to 60 minutes. Adherence to renal dose adjustments is critical for patient safety. |
Safety & Warnings
Common Side Effects
- Like all potent antimicrobial agents, imipenem/cilastatin (e.
- g.
- , Onem) can elicit a range of adverse reactions.
- Common side effects often include gastrointestinal disturbances such as nausea, vomiting, and diarrhea.
- Local reactions at the injection site, including phlebitis, pain, or erythema, are also frequently reported.
- Less common but potentially serious adverse effects involve hypersensitivity reactions, which can range from skin rashes and urticaria to severe anaphylaxis.
- Central nervous system adverse events, such as dizziness, confusion, tremors, myoclonic activity, and seizures, are particularly noteworthy, especially in patients with pre-existing CNS disorders or renal impairment.
- Hematologic abnormalities, including eosinophilia, leukopenia, neutropenia, and thrombocytopenia, can occur.
- Liver enzyme elevations (transaminases, alkaline phosphatase) have been observed.
- Additionally, Clostridioides difficile-associated diarrhea (CDAD) is a significant risk.
- Rare but severe cutaneous reactions like Stevens-Johnson syndrome have been documented.
- Patients should be closely monitored for any adverse reactions during therapy.
Serious Warnings
- Black Box Warning: While imipenem/cilastatin (e.g., Onem) does not carry a formal FDA-mandated Black Box Warning, healthcare professionals must be acutely aware of several significant safety concerns. Serious and occasionally fatal hypersensitivity reactions, including anaphylaxis, have been reported. Patients with a history of hypersensitivity to penicillins, cephalosporins, or other beta-lactams may be at increased risk due to potential cross-reactivity; a thorough allergy history is imperative. Furthermore, central nervous system (CNS) adverse effects, including seizures, confusion, and myoclonus, have occurred, particularly in patients with pre-existing CNS disorders (e.g., history of seizures, brain lesions) or impaired renal function where dosage adjustments were not adequately performed. Careful monitoring and appropriate dose modification based on renal function are critical to mitigate these risks. Clostridioides difficile-associated diarrhea (CDAD) can also occur and may range from mild to life-threatening. The development of drug-resistant bacteria due to inappropriate use is also a serious concern.
- While imipenem/cilastatin (e.
- g.
- , Onem) does not carry a formal FDA-mandated Black Box Warning, healthcare professionals must be acutely aware of several significant safety concerns.
- Serious and occasionally fatal hypersensitivity reactions, including anaphylaxis, have been reported.
- Patients with a history of hypersensitivity to penicillins, cephalosporins, or other beta-lactams may be at increased risk due to potential cross-reactivity; a thorough allergy history is imperative.
- Furthermore, central nervous system (CNS) adverse effects, including seizures, confusion, and myoclonus, have occurred, particularly in patients with pre-existing CNS disorders (e.
- g.
- , history of seizures, brain lesions) or impaired renal function where dosage adjustments were not adequately performed.
- Careful monitoring and appropriate dose modification based on renal function are critical to mitigate these risks.
- Clostridioides difficile-associated diarrhea (CDAD) can also occur and may range from mild to life-threatening.
- The development of drug-resistant bacteria due to inappropriate use is also a serious concern.
How it Works (Mechanism of Action)
Imipenem/cilastatin (e.g., Onem) exerts its bactericidal effect through a well-defined mechanism of action characteristic of the carbapenem class of antibiotics. Imipenem, the active antibacterial component, penetrates the bacterial cell wall and binds with high affinity to penicillin-binding proteins (PBPs), which are enzymes crucial for the synthesis and maintenance of the bacterial peptidoglycan cell wall. Specifically, imipenem primarily targets PBP-1 and PBP-2 in many susceptible bacteria. By irreversibly inhibiting these PBPs, imipenem disrupts the cross-linking of peptidoglycan chains, leading to a compromised, structurally weak bacterial cell wall. This defective cell wall results in osmotic instability, rapid cell lysis, and ultimately bacterial death. Its broad spectrum of activity against Gram-positive, Gram-negative, and anaerobic bacteria is attributed to its stability against most bacterial beta-lactamases, including extended-spectrum beta-lactamases (ESBLs). Cilastatin, the second component, is not antibacterial but serves as a renal dehydropeptidase-I inhibitor. This enzyme, found in the renal tubules, normally metabolizes imipenem, leading to reduced urinary concentrations and potential generation of nephrotoxic metabolites. Cilastatin prevents this degradation, thereby ensuring adequate imipenem concentrations in the urinary tract and reducing the risk of renal toxicity.