β-lactam antibiotics (beta-lactam antibiotics) are antibiotics that contain a beta-lactam ring in their chemical
structure. This includes penicillin derivatives (penams), cephalosporins and cephamycins (cephems), monobactams, carbapenems and carbacephems. Most β-lactam antibiotics work by inhibiting cell wall biosynthesis in the bacterial organism and are the most widely used group of antibiotics. Until 2003, when measured by sales, more than half of all commercially available antibiotics in use were β-lactam compounds. The first β-lactam antibiotic discovered, penicillin, was isolated from a strain of Penicillium rubens (named as Penicillium notatum at the time).
Bacteria often develop resistance to β-lactam antibiotics by synthesizing a β-lactamase, an enzyme that attacks the β-lactam ring. To overcome this resistance, β-lactam antibiotics can be given with β-lactamase inhibitors such as clavulanic acid.
β-lactam antibiotics are indicated for the prevention and treatment of bacterial infections caused by susceptible organisms. At first, β-lactam antibiotics were mainly active only against Gram-positive bacteria, yet the recent development of broad-spectrum β-lactam antibiotics active against various Gram-negative organisms has increased their usefulness.
In uninflamed (normal) brain meninges, the penetration of beta-lactam antibiotics is low, at 0.15 of AUCCSF/AUCS ratio (the ratio of area under curve of cerebrosopinal fluid against area under curve of serum).
Common adverse drug reactions for the β-lactam antibiotics include diarrhea, nausea, rash, urticaria, superinfection (including candidiasis).
Infrequent adverse effects include fever, vomiting, erythema, dermatitis, angioedema, pseudomembranous colitis.
Pain and inflammation at the injection site is also common for parenterally administered β-lactam antibiotics.
Immunologically mediated adverse reactions to any β-lactam antibiotic may occur in up to 10% of patients receiving that agent (a small fraction of which are truly IgE-mediated allergic reactions, see amoxicillin rash).