Β-lactams

Class of broad-spectrum antibiotics

Synonyms

β-lactam antibiotics

Drug Information
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Identifiers CAS Number PubChem DrugBank ChemSpider ID UNII KEGG ChEBI ChEMBL IUPAC Name		Chemical Data C H N O Molecular Weight

β-lactam antibiotics are a class of broad-spectrum antibiotics that contain a β-lactam ring in their molecular structures. This class includes several subgroups of antibiotics, such as penicillins, cephalosporins, carbapenems, and monobactams. β-lactams are the most widely used group of antibiotics and are effective against a wide range of bacteria.

Structure and Mechanism of Action

The defining feature of β-lactam antibiotics is the β-lactam ring, a four-membered lactam. This ring is crucial for the antibiotic's activity. β-lactams exert their antibacterial effect by inhibiting the synthesis of the bacterial cell wall. They achieve this by binding to and inactivating penicillin-binding proteins (PBPs), which are enzymes involved in the cross-linking of the peptidoglycan layer of the bacterial cell wall. This inhibition leads to cell lysis and death of the bacterium.

Subclasses of β-lactams

Penicillins

Penicillins were the first β-lactam antibiotics discovered and include drugs such as penicillin G, amoxicillin, and ampicillin. They are primarily effective against Gram-positive bacteria but have limited activity against Gram-negative bacteria.

Cephalosporins

Cephalosporins are a large group of β-lactam antibiotics that are divided into "generations" based on their spectrum of activity. First-generation cephalosporins, such as cephalexin, are effective against Gram-positive bacteria, while later generations, such as ceftriaxone and ceftazidime, have increased activity against Gram-negative bacteria.

Carbapenems

Carbapenems, such as imipenem and meropenem, are broad-spectrum β-lactams that are resistant to most β-lactamases. They are often used as "last-resort" antibiotics for severe infections caused by multidrug-resistant bacteria.

Monobactams

Monobactams, such as aztreonam, are unique among β-lactams in that they contain only a single β-lactam ring. They are effective primarily against Gram-negative bacteria and are often used in patients with penicillin allergies.

Resistance

Bacterial resistance to β-lactam antibiotics is a significant clinical problem. The most common mechanism of resistance is the production of β-lactamase enzymes, which hydrolyze the β-lactam ring, rendering the antibiotic ineffective. Other mechanisms include alterations in PBPs and reduced permeability of the bacterial cell wall.

Clinical Uses

β-lactam antibiotics are used to treat a wide variety of infections, including pneumonia, meningitis, sepsis, and urinary tract infections. They are often the first-line treatment for many bacterial infections due to their efficacy and safety profile.

Adverse Effects

While generally well-tolerated, β-lactam antibiotics can cause adverse effects, including allergic reactions, ranging from mild rashes to severe anaphylaxis. Other side effects may include gastrointestinal disturbances and, rarely, hematologic abnormalities.

Also see

• Antibiotic resistance
• Penicillin
• Cephalosporin
• Carbapenem
• Monobactam
• β-lactamase