Meronem NOT Tienam is favored in the setting of seizures
Meropenem (Meronem) is the second antipseudomonal carbapenem antibiotic to hit the market promoted by AstraZeneca, after imipenem/cilastatin (Tienam). Both Meronem and Tienam have similar antibacterial coverage, broad gram-positive and gram-negative aerobic and anaerobic coverage. But both drugs have "holes" in their coverage for MRSA (methicillin resistant Staph aureus), MRSE (methicillin resistant Staph epidermidis), enterococcus faecium, and stenotrophomonas (xanthomonas) maltophilia. Experts are debating how effective these drugs are against Legionella and atypicals (Chlamydia, Mycoplasma).
There is a difference between meropenem and imipenem. Meropenem is less likely to cause seizures. This makes it more useful for treating patients with meningitis and other preexisting CNS disorders. It is also approved for intra-abdominal infections. For now, Meronem is approved only for bacterial meningitis in children and intra-abdominal infections in both children and adults.
You will notice that Meronem doesn't contain cilastatin or a similar enzyme inhibitor like Tienam does. Tienam contains cilastatin to prevent the conversion of imipenem to a toxic metabolite in the kidney. Meronem doesn't need cilastatin because it isn't metabolized by this same enzyme.
| Table (1). Intravenous Meropenem (Meronem) Dose | |
|---|---|
| METHOD | DOSE |
| Traditional intermittent infusion method (over 30 minutes) | 500 mg every 6 hours or 1 to 2 g every 8 hours; 500 mg every 6 hours achieves comparable pharmacokinetic and pharmacodynamic parameters to 1 g every 8 hours. |
| Extended infusion method |
1 to 2 g every 8 hours over 3 hours. May give a loading dose of 1 to 2 g over 30 minutes, especially when rapid attainment of therapeutic drug concentrations is desired (e.g., sepsis). |
| Continuous infusion method |
2 g every 8 hours over 8 hours or 3 g every 12 hours over 12 hours. May give a loading dose of 1 to 2 g over 30 minutes, especially when rapid attainment of therapeutic drug concentrations is desired. |
- There are no clear differences in efficacy between imipenem and meropenem. The choice to use one over the other is predominantly based on toxicity profiles in specific hosts.
- As an example, meropenem is favored in the setting of seizures or pregnancy (see "Antibiotics use in pregnancy") because of the possible central nervous system toxicity and unknown safety in pregnancy of imipenem. Meropenem also may be easier to dose in the setting of changing or impaired renal failure.
References
- Alván, G., Nord, C.E. Adverse Effects of Monobactams and Carbapenems. Drug-Safety 12, 305–313 (1995).
- Zhanel GG, Simor AE, Vercaigne L, Mandell L; Canadian Carbapenem Discussion Group. Imipenem and meropenem: Comparison of in vitro activity, pharmacokinetics, clinical trials and adverse effects. Can J Infect Dis. 1998 Jul;9(4):215-28.