The pharmacologic agent cefalexin is an antibiotic used to treat bacterial infections. Cefalexin can be applied orally and belongs to the antibiotic group of cephalosporins.
What is cefalexin?
As a cephalosporin, cefalexin belongs to the so-called beta-lactams, which are industrially produced semisynthetically. It is a prescription antibiotic in Germany. After ingestion of a tablet containing the active ingredient cefalexin, absorption occurs rapidly via the mucous membranes of the gastrointestinal tract. The half-life in the bloodstream is about 1 hour. Cefalexin also passes through the liver cells in the process, but is not degraded or changed in chemical structure, as are many other antibiotics. At the end of its half-life in blood plasma, cefalexin is therefore excreted completely and unmetabolized in the urine via both kidneys. The molecular weight of the antibiotic cefalexin is approximately 348 g/mol. The multipeptide cefalexin consists of the chemical elements carbon, hydrogen, nitrogen, oxygen, and sulfur.
Pharmacologic action
The antibiotic is used against germs that exhibit sensitivity to cefalexin. As a so-called broad-spectrum antibiotic, cefalexin is effective against a wide range of bacterial pathogens. An effect on viruses, on the other hand, is excluded. After oral administration, the active ingredient is rapidly distributed via the vascular system to all organs and tissues; the effect of the antibiotic is therefore systemic. Cefalexin selectively intervenes directly in the multiplication of pathological bacteria by depositing in the cell wall. As a result, the cell wall synthesis of these bacteria is inhibited and they are therefore no longer able to divide independently and thus die. This is because the cell wall of pathogenic bacteria must be intact for the metabolism of these pathogens to function smoothly. After being incorporated into the cell wall of the bacteria, cefalexin blocks the synthesis of peptidoglycan, but this low-molecular protein is essential for the stability of the bacteria cell wall. The antibiotic cefalexin therefore ensures that the structural integrity of the bacterial cell wall can no longer be achieved. The immediate consequence is the death of the bacteria in the infected areas of the body. Cefalexin thus acts through its direct intervention in the metabolism of the pathogenic bacteria.
Medical use and application
In medical use, the broad-spectrum antibiotic cefalexin is particularly effective against so-called gram-positive bacteria. These bacterial strains include, for example, staphylococci, streptococci, coliform bacteria, or klebsiae. As a special feature, cefalexin has an enterococci gap that must be taken into account during treatment. Cefalexin is therefore explicitly not effective against enterococci, as their cell wall differs greatly in chemical composition from other gram-positive germs. The effect of cefalexin relates exclusively to bacteria. It has been proven many times that cefalexin has no effect against mycoplasma, chlamydia or multi-resistant germs (MRSA). The main indications for oral treatment with cefalexin are bacterial infections of the upper respiratory tract, such as tonsillitis or laryngitis. Pneumonia caused by bacteria also responds well to treatment with cefalexin, as long as the active ingredient can be administered orally. Administration of the active ingredient cefalexin by infusion is contraindicated. Other typical indications are bacterial middle ear infections, urinary tract infections caused by gram-positive bacteria, and bacterial infections of the skin. Infections of the soft tissues and bones located deeper in the organism are also generally amenable to treatment with cefalexin. Therefore, for example, chronic inflammation of the bones, osteomyelitis, joint inflammation or phlegmon can also be treated with the active substance. Cefalexin diffuses into the body tissues via the bloodstream and can thus kill the pathogenic germs on the spot, even in chronic courses. In the case of these non-acute infections, however, particular attention must be paid to the duration of therapy and dose in order not to jeopardize the success of treatment and to effectively prevent resistance.
Risks and side effects
As with many other antibiotics, cefalexin administration can cause resistance to develop. The antibiotic would then no longer work. To prevent the development of bacterial resistance, cefalexin should always be taken for a sufficiently long time and at an appropriate dosage calculated according to body weight if prescribed. In case of known hypersensitivity reactions to cefalexin, the active substance must not be used. Adverse body reactions and side effects may occur, especially at the beginning of treatment. Most adverse effects due to cefalexin relate to gastrointestinal disorders with symptoms such as nausea, vomiting, or diarrhea. Whether the drug should be discontinued when such side effects occur must be decided by the physician on a case-by-case basis. Other known side effects also include dizziness and disturbances of the electrolyte balance. Cross-resistance may also occur if penicillin is administered at the same time. In urine tests, the presence of cefalexin in the urine may temporarily falsify diagnostic values.
