Mechanism of action and spectrum of activity
Meropenem belongs to beta-lactam antibiotics, representing a potent subgroup of carbapenems (alongside imipenem and ertapenem). Like other beta-lactams, it has a bactericidal effect by disrupting bacterial cell wall synthesis.
The spectrum of activity of meropenem has important clinical features when compared to the "gold standard" imipenem:
- It demonstrates higher efficacy against Gram-negative flora.
- At the same time, its activity against Gram-positive cocci (staphylococci and streptococci) is somewhat lower than that of imipenem.
- Unlike ertapenem (Invanz), which is inferior to other carbapenems in combating non-fermenting Gram-negative bacteria (Pseudomonas aeruginosa, Acinetobacter), meropenem remains highly relevant for severe hospital-acquired infections.
Pharmacokinetics: key difference from imipenem
Historically, the first carbapenem—imipenem (a derivative of thienamycin produced by Streptomyces cattleya)—has a serious pharmacokinetic drawback. In the renal tubules, it is rapidly degraded by a specific enzyme, dehydropeptidase I. Because of this, a therapeutic concentration of the antibiotic is not achieved in the urine, and imipenem monotherapy is ineffective. The problem is solved by combining imipenem with cilastatin (drugs Tienam, Primaxin), an enzyme inhibitor that does not kill bacteria itself but protects the antibiotic.
The main advantage of meropenem is that its molecule is inherently resistant to the action of renal dehydropeptidase I. Consequence: Meropenem is used as an independent drug. It does not require cilastatin to maintain high concentrations in the body.
Indications and special usage instructions
The drug is available as a powder in 0.5 and 1.0 g vials.
The route of administration is strictly limited: meropenem is administered intravenously only (as an infusion or bolus). Unlike ertapenem, there is no intramuscular formulation for meropenem.
- Standard dosing regimen: intravenous infusion of 0.5–1.0 g every 8 hours.
- Limitations: According to clinical data, meropenem is not used for infectious lesions of the osteoarticular system.
Side effects and safety
An important clinical advantage of meropenem over imipenem is its central nervous system safety profile. Meropenem lacks convulsive activity, making it a safer choice for patients with neurological pathology or a high risk of seizures.
Drug interactions
When prescribing meropenem, two critically important interactions must be considered:
- Probenecid: when co-administered, it increases the plasma concentration of meropenem.
- Valproic acid: all carbapenems (imipenem, meropenem, ertapenem) clinically significantly reduce blood levels of sodium valproate. This requires extreme caution when prescribing the drug to patients with epilepsy, as a sharp drop in anticonvulsant concentration can trigger a seizure.
Sample prescription
Example of prescribing meropenem for intravenous infusion:
Rp.: Meropenemi 1,0 D.t.d. N. 10 S. Intravenously as an infusion, after dissolving in saline, every 8 hours.
Briefly: answers to topical questions
For which specific infectious diseases is the prescription of meropenem indicated?
Meropenem is prescribed for severe infections in empirical therapy, multidrug-resistant or extensively drug-resistant tuberculosis when a standard regimen cannot be formulated, generalized forms of meningococcal infection with a severe course or allergy, as well as severe lung abscess.
What side effects does meropenem cause?
- Hypersensitivity.
- Seizures.
- Nausea and vomiting.
- Diarrhea.
- Impaired liver and kidney function.
Is meropenem active against MRSA (methicillin-resistant Staphylococcus aureus)?
Carbapenems, including meropenem, are not active against methicillin-resistant staphylococci.
MEROpenem — MErner convulsive activity (lower), MErner kidney dependence / no cilastatin needed, MErner activity against Gram(+) cocci, but powerful against Gram(-).
Class and exam questions
Why is imipenem prescribed with cilastatin, while meropenem is given alone?
Imipenem is degraded in the kidneys by the enzyme dehydropeptidase I, thus requiring protection with cilastatin. Meropenem is resistant to this enzyme and works effectively as a single agent.
Can meropenem be administered intramuscularly?
No, the drug is administered exclusively intravenously (infusion or bolus). There is no intramuscular formulation of meropenem.
How does meropenem affect epilepsy patients taking valproates?
Meropenem sharply reduces the blood concentration of valproic acid, which can lead to loss of seizure control. Meanwhile, the antibiotic itself does not possess convulsive activity.
Is meropenem used to treat osteomyelitis?
No, according to pharmacological guidelines, meropenem is not used for infections of the osteoarticular system.
What else to study on this topic
- Mechanism of action of beta-lactam antibiotics on the bacterial cell wall
- Comparative characteristics of carbapenems: imipenem, meropenem, ertapenem
- The role of renal dehydropeptidase I in drug metabolism
- Mechanisms of interaction between carbapenems and valproic acid
- Non-fermenting Gram-negative bacteria (P. aeruginosa, Acinetobacter) and antibiotic selection
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