1. Pharmacology:

  • Mechanism of Action: Cephalexin is a cephalosporin antibiotic that works by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins, interfering with cell wall formation, leading to bacterial cell death.

  • Spectrum of Activity: It is active against many gram-positive and some gram-negative bacteria.

2. Indications:

  • Respiratory tract infections (e.g., pneumonia, bronchitis)

  • Urinary tract infections (e.g., cystitis, pyelonephritis)

  • Skin and soft tissue infections

  • Bone infections

  • Ear infections (otitis media)

  • Streptococcal infections

  • Some types of gastro-intestinal infections

3. Dosage & Administration:

  • Adults:

    • For most infections: 250–500 mg every 6 hours.

    • Severe infections may require 1–2 grams every 6 hours.

  • Pediatric Dosage:

    • Typically 25–50 mg/kg/day in divided doses every 6–12 hours.

  • Cephalexin can be taken with or without food. The capsule form is typically taken with a full glass of water.

  • Dosage adjustments may be necessary for patients with renal impairment.

4. Interactions:

  • Probenecid: May increase cephalexin levels by reducing renal excretion.

  • Anticoagulants (e.g., warfarin): Cephalexin may increase the risk of bleeding.

  • Other Antibiotics: Concurrent use with other antibiotics (especially bacteriostatic ones like tetracyclines) may reduce efficacy.

  • Metformin: May increase the risk of lactic acidosis in some patients.

5. Contraindications:

  • Known hypersensitivity to cephalosporins or penicillin.

  • Severe renal impairment (unless dosage adjustment is made).

  • History of allergic reactions to cephalexin or other beta-lactam antibiotics.

6. Side Effects:

  • Common: Diarrhea, nausea, vomiting, abdominal pain.

  • Serious: Allergic reactions (rash, anaphylaxis), Clostridium difficile-associated diarrhea, jaundice, liver toxicity, renal dysfunction, blood disorders (e.g., thrombocytopenia).

  • Rare: Seizures, Stevens-Johnson syndrome, hemolytic anemia.

7. Pregnancy & Lactation:

  • Pregnancy: Category B (no evidence of harm in humans). Cephalexin is generally considered safe during pregnancy, but it should be used only if clearly needed.

  • Lactation: Cephalexin is excreted in breast milk in small amounts. While generally considered safe for use during breastfeeding, a pediatrician should be consulted before use.

8. Precautions & Warnings:

  • Use with caution in patients with a history of gastrointestinal diseases, especially colitis.

  • Caution is also required in patients with renal impairment (dose adjustment needed).

  • Discontinue if allergic reactions occur.

  • Monitor for signs of superinfection (e.g., fungal infections or Clostridium difficile).

  • Use with caution in patients with a history of seizure disorders.

9. Overdose Effects:

  • Symptoms of overdose may include nausea, vomiting, diarrhea, stomach pain, and in severe cases, seizures or kidney problems.

  • Treatment for overdose is symptomatic and supportive. Dialysis may be required in cases of severe overdose.

10. Therapeutic Class:

  • Cephalexin belongs to the antibiotic class and is specifically a first-generation cephalosporin.

11. Storage Conditions:

  • Cephalexin should be stored at room temperature (20–25°C or 68–77°F), away from moisture and heat.

  • The oral suspension should be refrigerated and used within 14 days of preparation.

  • Protect from light.

12. Chemical Structure:

  • Molecular Formula: C16H17N3O4S

  • IUPAC Name: 7-(D-α-Amino-α-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid

  • The chemical structure of cephalexin includes a beta-lactam ring, which is characteristic of cephalosporins, essential for its antibacterial action.

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