Description

Cefixime is a broad-spectrum, third-generation cephalosporin antibiotic. Unlike some other cephalosporins, it is an orally administered drug, available in tablet, capsule, chewable tablet, and liquid suspension forms. This makes it a convenient option for treating infections in outpatient settings. Cefixime is bactericidal, meaning it works by directly killing bacteria. It is effective against a variety of Gram-positive and Gram-negative bacteria and, like other third-generation cephalosporins, it is stable against many beta-lactamase enzymes produced by bacteria.

Indications

Cefixime is used to treat a range of bacterial infections. Its indications include:

• Upper Respiratory Tract Infections: Such as tonsillitis and pharyngitis.

• Lower Respiratory Tract Infections: Including acute exacerbations of chronic bronchitis.

• Urinary Tract Infections (UTIs): For complicated and uncomplicated UTIs caused by susceptible organisms.

• Otitis Media: (Middle ear infections) in children and adults.

• Gonorrhea: Cefixime is a treatment option for uncomplicated urogenital, anorectal, or pharyngeal gonorrhea, although it is often considered a second-line treatment to ceftriaxone.

• Typhoid Fever: It is sometimes used off-label for the treatment of typhoid fever.

Mechanism of Action

Cefixime’s mechanism of action is characteristic of the beta-lactam class of antibiotics. It works by interfering with the synthesis of the bacterial cell wall, which is essential for the survival and integrity of bacterial cells. The process can be broken down into the following steps:

1. Inhibition of Penicillin-Binding Proteins (PBPs): Cefixime, like other cephalosporins, has a chemical structure that includes a beta-lactam ring. This ring binds to and inhibits a group of enzymes called penicillin-binding proteins (PBPs), which are found in the bacterial cell membrane.

2. Prevention of Peptidoglycan Cross-linking: PBPs are crucial for the final stages of bacterial cell wall synthesis. They catalyze the transpeptidation reaction, which cross-links the peptidoglycan chains to create a strong, rigid cell wall. By binding to PBPs, cefixime prevents this critical cross-linking from occurring.
3. Cell Wall Instability: Without proper cross-linking, the bacterial cell wall becomes weak and structurally unsound. It is unable to withstand the high osmotic pressure from within the cell.
4. Lysis and Cell Death: This structural instability leads to the activation of autolytic enzymes within the bacterial cell, which cause the cell to swell and eventually lyse (burst). This process directly kills the bacteria, thus producing a bactericidal effect.

Cefixime is effective against many bacteria that have become resistant to older antibiotics because its beta-lactam ring is more resistant to degradation by beta-lactamase enzymes.