Cephalexin: Full Review
Cephalexin is a first-generation cephalosporin antibiotic used to treat a variety of bacterial infections. It is known for its effectiveness against Gram-positive bacteria and some Gram-negative bacteria.
1. Mechanism of Action
Cephalexin works by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs) on the bacterial cell wall, which interferes with the formation of cross-links between peptidoglycan layers. This disruption weakens the cell wall, leading to bacterial lysis and death. Cephalexin is bactericidal, meaning it kills bacteria rather than merely inhibiting their growth.
2. Uses
Cephalexin is used to treat a variety of infections, including:
- Skin and Soft Tissue Infections: Such as cellulitis, impetigo, and wound infections.
- Upper Respiratory Tract Infections: Including pharyngitis and tonsillitis.
- Otitis Media: Ear infections in children.
- Urinary Tract Infections (UTIs): Including cystitis and pyelonephritis.
- Bone and Joint Infections: For example, osteomyelitis.
Cephalexin is often used for mild to moderate infections and as prophylaxis before certain types of surgeries.
3. Dosage and Administration
Cephalexin is typically administered orally in the form of capsules, tablets, or suspension. The usual dosage varies based on the infection being treated:
- Adults: 250 mg to 500 mg every 6 to 12 hours, depending on the severity of the infection.
- Children: Dosing is based on weight and the type of infection, often ranging from 25 mg/kg to 50 mg/kg per day, divided into multiple doses.
4. Contraindications
Cephalexin is contraindicated in:
- Patients with hypersensitivity to cephalosporins or penicillins (due to potential cross-reactivity).
- Patients with a history of severe allergic reactions to beta-lactam antibiotics.
- Severe renal impairment: Dose adjustments are required for patients with significant kidney dysfunction.
5. Side Effects
Common side effects of cephalexin include:
- Gastrointestinal issues: Nausea, vomiting, diarrhea, and abdominal pain.
- Allergic reactions: Rash, itching, and anaphylaxis in rare cases.
- Hematologic effects: Rarely, leukopenia, thrombocytopenia, or eosinophilia.
- Renal effects: Rare instances of interstitial nephritis or acute kidney injury.
- Superinfection: Prolonged use can lead to the overgrowth of resistant organisms, such as yeast infections.
6. Drug Interactions
- Anticoagulants: Cephalexin can enhance the effects of anticoagulants like warfarin, increasing the risk of bleeding.
- Probenecid: Can increase cephalexin levels by inhibiting its renal excretion.
- Other nephrotoxic drugs: Use with caution in combination with other drugs that can affect kidney function.
7. Special Precautions
- Renal Function: Dose adjustments are needed for patients with impaired kidney function to prevent toxicity.
- Allergies: Patients with a history of penicillin allergy should be monitored for potential cross-reactivity with cephalosporins.
- Superinfections: Long-term use may lead to the development of resistant organisms or fungal infections.
8. Resistance
Resistance to cephalexin can develop through several mechanisms:
- Beta-lactamase production: Enzymes that break down cephalexin, reducing its effectiveness.
- Altered PBPs: Bacteria may alter their PBPs to reduce cephalexin binding.
- Efflux pumps: Some bacteria may pump cephalexin out of the cell before it can act.
9. Storage and Stability
Cephalexin should be stored at room temperature, away from moisture and heat. The oral suspension should be refrigerated and used within 14 days.
10. Summary
Cephalexin is a first-generation cephalosporin effective against a range of bacterial infections, especially those caused by Gram-positive organisms. It is commonly used for skin, respiratory, urinary tract, and bone infections. Despite its effectiveness, cephalexin can cause side effects such as gastrointestinal disturbances and allergic reactions. Careful consideration of patient allergies, renal function, and potential drug interactions is essential for safe and effective use.
