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  • Cephalexin: Drug Information

    Cephalexin is a broad-spectrum antibiotic that is used to treat bacterial infections caused by susceptible bacteria. It is commonly used to treat the following infections:

    • Skin infections such as cellulitis, impetigo, and folliculitis
    • Urinary tract infections (UTIs) such as cystitis and pyelonephritis
    • Respiratory tract infections such as streptococcal pharyngitis, tonsillitis, and pneumonia
    • Bone and joint infections such as osteomyelitis and septic arthritis
    • Ear infections such as otitis media and otitis externa

    Cephalexin may also be used to prevent certain types of bacterial infections, such as in people who are at high risk of developing an infection after surgery. However, it is important to note that cephalexin is not effective against all types of bacteria and should only be used to treat bacterial infections, not viral or fungal infections. The specific use of cephalexin will depend on the individual patient’s condition and the judgment of their healthcare provider. See our selection of cephalexin impurities in our catalog.

    What is cephalexin?

    Cephalexin is a broad-spectrum antibiotic belonging to the class of first-generation cephalosporins. It is commonly prescribed to treat bacterial infections such as skin infections, urinary tract infections, respiratory tract infections, bone and joint infections, and ear infections. Cephalexin works by interfering with the cell wall synthesis of bacteria, ultimately leading to bacterial death. It is available in both oral capsule and liquid forms and is typically taken two to four times daily depending on the severity of the infection being treated. As with any medication, it is important to take cephalexin exactly as prescribed by a healthcare provider and to complete the full course of treatment, even if symptoms improve before the medication is finished.

    How does cephalexin work?

    Cephalexin works by interfering with the cell wall synthesis of bacteria. Bacteria have a protective cell wall that surrounds the cell membrane, providing structural support and protection against environmental stressors. Cephalexin belongs to a class of antibiotics known as cephalosporins, which are beta-lactam antibiotics that work by inhibiting the formation of peptidoglycan cross-links in bacterial cell walls. Peptidoglycan is a key component of the bacterial cell wall, and the cross-linking of peptidoglycan chains provides the strength and rigidity necessary for the bacterial cell wall to function properly.

    Cephalexin works by binding to and inhibiting the activity of enzymes known as penicillin-binding proteins (PBPs), which are responsible for the cross-linking of peptidoglycan chains in bacterial cell walls. By interfering with this process, cephalexin weakens the cell wall, making it more susceptible to osmotic pressure and ultimately leading to bacterial cell death.

    Cephalexin is effective against a wide range of bacteria, including gram-positive and some gram-negative bacteria, but is not effective against all types of bacteria or against infections caused by viruses or fungi. It is important to note that overuse or misuse of antibiotics, including cephalexin, can lead to the development of antibiotic-resistant bacteria.

    Chemical properties of cephalexin

    Cephalexin, also known by its chemical name 7-(D-alpha-Amino-alpha-phenyl acetamido)-3-methyl-3-cephem-4-carboxylic acid monohydrate, has the following chemical properties:

    • Molecular formula: C16H17N3O4S•H2O
    • Molecular weight: 365.41 g/mol (anhydrous form)
    • Solubility: Cephalexin is soluble in water, sparingly soluble in methanol, and practically insoluble in ethanol and chloroform.
    • Melting point: The melting point of cephalexin monohydrate is reported to be between 215°C to 221°C.
    • Appearance: Cephalexin is a white or off-white crystalline powder or granular substance.
    • Stability: Cephalexin is stable under normal storage conditions and does not undergo significant degradation or decomposition. However, it should be stored in a cool, dry place and protected from light and moisture to maintain its stability.

    Cephalexin is classified as a beta-lactam antibiotic and is structurally similar to other beta-lactam antibiotics such as penicillins and cephalosporins. It contains a beta-lactam ring that is essential for its antibacterial activity, as it inhibits the synthesis of the bacterial cell wall.

    Potential side effects and precautions of cephalexin

    As with any medication, cephalexin can cause side effects, although not everyone experiences them. Some potential side effects of cephalexin include:

    • Nausea, vomiting, diarrhea
    • Stomach pain or discomfort
    • Headache
    • Dizziness
    • Skin rash or itching
    • Joint pain
    • Vaginal itching or discharge

    In rare cases, cephalexin can cause more severe side effects such as:

    • Severe allergic reactions (including anaphylaxis)
    • Stevens-Johnson syndrome (a severe skin reaction)
    • Clostridium difficile-associated diarrhea (a severe intestinal infection)

    It is important to seek medical attention immediately if any of these symptoms occur.

    Cephalexin may also interact with other medications, so it is important to inform a healthcare provider of any other medications or supplements being taken.

    Precautions that should be taken while using cephalexin include:

    • Informing a healthcare provider of any allergies or previous adverse reactions to cephalosporin antibiotics or penicillin antibiotics
    • Informing a healthcare provider of any pre-existing medical conditions such as kidney disease, colitis, or other gastrointestinal problems
    • Taking cephalexin exactly as prescribed, and completing the full course of treatment as directed
    • Not taking cephalexin for viral infections such as the common cold or flu, as it is only effective against bacterial infections

    Overall, cephalexin is considered safe and effective when used appropriately and under the guidance of a healthcare provider.

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