C-LEX 500

Indications

• Skin and soft tissue infections
• Respiratory tract infections
• Urinary tract infections
• Bone infections
• Otitis media

Dosage

Children: For children, the usual dosage is 25-50 mg/kg/day in divided doses, depending on the type and severity of the infection. Refer to the BNF for Children for specific dosing recommendations.

Adults: The usual adult dose is 500 mg every 6 hours, or 750 mg every 12 hours, depending on the severity of the infection. The maximum daily dose should not exceed 4 g.

Mechanism of action

Cephalexin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins located in the bacterial cytoplasmic membrane. This inhibition prevents the cross-linking of peptidoglycan chains, which are essential for maintaining bacterial cell wall strength and rigidity. As a result, bacterial growth and cell division are inhibited, leading to cell lysis, particularly in rapidly dividing bacteria.

Pharmacodynamics

Cephalexin exhibits bactericidal activity, primarily targeting gram-positive bacteria. It functions by disrupting the synthesis of the bacterial cell wall, which is a critical process for bacterial survival and proliferation. The drug is effective in treating superficial infections that often arise from minor wounds or lacerations, making it a commonly prescribed antibiotic in various clinical settings.

Pharmacokinetics

Cephalexin is rapidly absorbed from the gastrointestinal tract, with peak plasma concentrations occurring within 1 hour after oral administration. It is widely distributed throughout the body, including in tissues and body fluids. The drug is primarily excreted unchanged in the urine, with a half-life of approximately 0.5 to 1 hour. Renal function may influence the elimination of cephalexin, thus dose adjustments may be necessary in patients with impaired renal function.

Contra-indications

• Hypersensitivity to cephalexin or other cephalosporins
• History of severe allergic reactions to penicillins

Adverse effects

• Nausea
• Vomiting
• Diarrhea
• Rash
• Allergic reactions
• Severe skin reactions
• Elevated liver enzymes
• Superinfection with resistant organisms

Interactions

• Probenecid may increase serum levels of cephalexin
• May reduce the effectiveness of oral contraceptives

Precautions

• Caution in patients with renal impairment
• Caution in patients with a history of gastrointestinal disease, especially colitis
• Monitor for signs of anaphylaxis in patients with a history of penicillin allergy

Pregnancy

Cephalexin is categorized as pregnancy category B; it should be used during pregnancy only if clearly needed.

Breast-feeding

Cephalexin is excreted in breast milk; caution should be exercised when administering to nursing mothers.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• Capsules
• Tablets
• Oral suspension

Mechanism of action

Cephalexin is a first generation cephalosporin antibiotic. Cephalosporins contain a beta lactam and dihydrothiazide. Unlike penicillins, cephalosprins are more resistant to the action of beta lactamase. Cephalexin inhibits bacterial cell wall synthesis, leading breakdown and eventualy cell death. CEPHALOTHIN & ITS CONGENERS INHIBIT BACTERIAL CELL-WALL SYNTHESIS IN MANNER SIMILAR TO THAT OF PENICILLIN. /CEPHALOSPORINS/ The penicillins and their metabolites are potent immunogens because of their ability to combine with proteins and act as haptens for acute antibody-mediated reactions. The most frequent (about 95 percent) or "major" determinant of penicillin allergy is the penicilloyl determinant produced by opening the beta-lactam ring of the penicillin. This allows linkage of the penicillin to protein at the amide group. "Minor" determinants (less frequent) are the other metabolites formed, including native penicillin and penicilloic acids. /Penicillins/ Bactericidal; action depends on ability to reach and bind penicillin-binding proteins located in bacterial cytoplasmic membranes; cephalosporins inhibit bacterial septum and cell wall synthesis, probably by acylation of membrane-bound transpeptidase enzymes. This prevents cross-linkage of peptidoglycan chains, which is necessary for bacterial cell wall strength and rigidity. Also, cell division and growth are inhibited, and lysis and elongation of susceptible bacteria frequently occur. Rapidly dividing bacteria are those most susceptible to the action of cephalosporins. /Cephalosporins/ CEPHALOSPORIN C IS VERY RESISTANT TO ACTION OF PENICILLINASE, FOR WHICH IT IS BOTH COMPETITIVE & NONCOMPETITIVE INHIBITOR, DEPENDING ON SUBSTRATE TESTED... /CEPHALOSPORINS/

Pharmacodynamics

Cephalexin (also called Cefalexin) is a first generation cephalosporin antibiotic. It is one of the most widely prescribed antibiotics, often used for the treatment of superficial infections that result as complications of minor wounds or lacerations. It is effective against most gram-positive bacteria through its inihibition of the cross linking reaction between N-acetyl muramicacid and N-acetylglucosamine in the cell wall, leading to cell lysis.