Β-lactam antibiotic
Beta-lactam antibiotics are a type of antibiotics that penicillins and the non-penicillin drugs such as cephalosporins, penems, monobactams.
Structure[edit | edit source]
They share a basic chemical structure that includes a three-carbon, one-nitrogen cyclic amine structure known as the beta-lactam ring. The side chain associated with the beta-lactam ring is a variable group attached to the core structure by a peptide bond; the side chain variability contributes to antibacterial activity. As of the date of this publication, FDA has approved over 34 beta-lactam compounds as active ingredients in drugs for human use.
Classes[edit | edit source]
Beta-lactam antibiotics include the following five classes:
- penicillins (e.g., ampicillin, oxacillin)
- cephalosporins (e.g., cephalexin, cefaclor)
- penems (e.g., imipenem, meropenem)
- carbacephems (e.g., loracarbef)
- monobactams (e.g., aztreonam)
Clinical importance[edit | edit source]
Since the β-lactam ring is part of the core structure of several antibiotic families such as penicillins, cephalosporins, carbapenems, and monobactams, they are an important class of antibiotics.
Mechanism of action[edit | edit source]
The betalactams work by inhibiting bacterial cell wall biosynthesis. This has a lethal effect on bacteria.
Antibiotic resistance[edit | edit source]
Many bacteria populations will typically contain a subgroup that is resistant to β-lactam antibiotics
Allergies[edit | edit source]
- Allergic reactions associated with penicillins and non-penicillin beta-lactams range from rashes to life-threatening anaphylaxis.
- Immunoglobulin E (IgE) antibodies mediate the immediate hypersensitivity reactions that are responsible for the symptoms of hay fever, asthma, hives, and anaphylactic shock.
- IgE-mediated hypersensitivity reactions are of primary concern because they may be associated with significant morbidity and mortality.
- Patients with a history of hypersensitivity to penicillin may also experience IgE-mediated reactions to other beta-lactams, such as cephalosporins and penems.
Cross sensitivity[edit | edit source]
- All non-penicillin beta-lactams also have the potential to sensitize individuals, and subsequent exposure to penicillin may result in severe allergic reactions in some patients.
- Although the frequency of hypersensitivity reactions due to cross-reactivity between beta-lactam classes can be lower than the risk within a class, the hazard posed is present11 and potentially life-threatening.
- The potential health hazard of non-penicillin beta-lactams therefore is similar to that of penicillins.
No minimum threshold dose known[edit | edit source]
• It is difficult to define the minimal dose below which allergic responses are unlikely to occur in humans. • There is a lack of suitable animal or receptor testing models that are predictive of human sensitivity. • The threshold dose at which allergenic response could occur is extremely low and difficult to detect with current analytical methods.
Beta-Lactamase Inhibitors[edit | edit source]
- Beta-lactam compounds such as clavulanic acid, tazobactam, and sulbactam have weak antibacterial activity but are irreversible inhibitors of many beta-lactamases.
- These compounds, which are potential sensitizing agents, are typically used in combination with specific betalactam agents to preserve antibacterial activity (e.g., amoxicillin-clavulanate, piperacillin-tazobactam).
- Because these compounds are almost always used in combination with specific beta-lactam agents, any clinical observations of hypersensitivity reactions likely would be attributed to the beta-lactam antibiotic component rather than the inhibitor.
- Although there have been no case reports confirming anaphylactic reactions to a beta-lactamase inhibitor that is also a beta-lactam, these compounds are potentially sensitizing agents, and manufacturers should implement controls to reduce the risk of cross-contamination with beta-lactamase inhibitors as with all other beta-lactam products.
Beta-Lactam Intermediates and Derivatives[edit | edit source]
Some beta-lactam intermediate compounds and derivatives also possess similar sensitization and cross–reactivity properties. Beta-lactam intermediate compounds usually are API precursor materials that undergo molecular change or purification before use in the manufacture of betalactam antibiotic APIs. As a result of these changes, the intermediate compounds may develop antigenic characteristics that can produce allergic reactions.
Intermediates[edit | edit source]
- 6-aminopenicillanic acid (6-APA) serves as the intermediate for the formation of all synthetic penicillins that are formed by attaching various side chains.
- The structure of 6-APA includes unbroken beta-lactam and thiazolidine rings. The beta-lactam ring is relatively unstable, and it commonly breaks open.
- In the case of 6-APA, this breakage leads to the formation of a penicilloyl moiety, which is the major antigenic determinant of penicillin. This moiety is thought to be a common cause of penicillin urticarial reaction.17 Degradation of 6-APA can also result in the formation of minor
- antigenic determinants, including penicilloic acids, penaldic acid, and penicillamine.
Cause of anaphylaxis[edit | edit source]
Anaphylactic reactions to penicillins usually are due to the presence of IgE antibodies to minor determinants in the body. Although 6-APA is not a true antibiotic, it still carries with it a potential to induce allergenicity.
Derivatives[edit | edit source]
- Derivatives are unintended by-products that occur during the manufacturing process (i.e., an impurity or degradant).
- Like intermediates, beta-lactam derivatives could have sensitizing properties and may develop antigenic properties that can produce allergic reactions.
Beta-lactam manufacturing[edit | edit source]
- Beta-lactam chemical manufacturing processes including, but not limited to, fermentation and synthesis, may create beta-lactam intermediates or derivatives with unknown health consequences.
- Although the health risk of sensitization and cross-reaction is difficult to predetermine for beta-lactam intermediates and derivatives and is not always well-defined, manufacturing controls intended to reduce the risk of cross-contamination should be considered for operations that produce beta-lactam intermediates or derivatives.
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