Antibiotics - Carbapenems and monobactams: Nursing pharmacology

Carbapenems and monobactams are beta-lactam antibiotics, which means that they have a characteristic beta-lactam ring in their structure. However, due to their widespread use, some bacteria have acquired resistance to many beta-lactams by developing enzymes called beta-lactamases, which latches on to the beta-lactam ring and degrades the antibiotic. For this reason, carbapenems and monobactams have a slight modification in their beta-lactam ring structure, which makes them less susceptible to beta-lactamases.

Now, carbapenems can be used to treat serious infections, such as complicated appendicitis, peritonitis, soft-tissue infections, bacterial meningitis, as well as gynecological infections, pyelonephritis, and bacteremia. Carbapenems have a wide range of action against gram-positive bacteria like methicillin-sensitive Staphylococcus aureus, Streptococcus pneumoniae, and group A beta-hemolytic streptococci; and gram-negative bacteria like Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella spp, Neisseria spp, and Acinetobacter spp.

On the other hand, monobactams are only useful in the treatment of gram-negative bacterial species, and are primarily used to treat clients with cystic fibrosis who have pulmonary Pseudomonas aeruginosa infections.

Starting with carbapenems, the most commonly used ones include doripenem, ertapenem, meropenem, as well as meropenem-vaborbactam, a combination of meropenem and vaborbactam, a beta-lactamase inhibitor, which further increases the spectrum of activity, and imipenem-cilastatin, a combination of carbapenem and the dipeptidase inhibitor cilastatin which prevents imipenem from being broken down, prolonging its antibacterial effect. Now, all of the carbapenems are administered intravenously, and ertapenem can also be given intramuscularly.

Moving on to monobactams, the only medication in this group is aztreonam, which is only given via inhalation. Once administered, carbapenems and monobactams work by binding to and inhibiting a bacterial enzyme called DD-transpeptidase, or penicillin-binding proteins, or PBPs for short, which bacteria need to build their cell walls. As a result, carbapenems and monobactams act by inhibiting bacterial cell wall synthesis, which ultimately kills the bacteria.

Common side effects of carbapenems and monobactams include gastrointestinal disturbances, like nausea, vomiting, and hypersensitivity reactions. These medications can also disrupt the normal bacterial flora, increasing the risk of superinfections like Clostridioides difficile infection, as well as oral and vaginal candidiasis.

Clients taking these medications may also experience central nervous system disturbances like headaches, confusion, and even seizures. Some clients may present with serious hypersensitivity reactions, such as Stevens-Johnson syndrome, toxic epidermal necrolysis, angioedema, and even anaphylaxis. Finally, when given via injection, these medications can cause injection site reactions like pain, redness, and even thrombophlebitis; while aztreonam administered via inhalation can cause cough, bronchospasm, and sore throat.

Now, carbapenems and monobactams are contraindicated in clients allergic to any beta-lactam antibiotic due to the risk of cross-reactivity between the different classes. Carbapenems and monobactams should be used with caution in clients with a history of seizures and during pregnancy and breastfeeding. Additional precautions should be taken in clients with renal disease.