Cephalexin
Keflex
Overview
Cephalexin is a first-generation oral cephalosporin antibiotic used to treat susceptible bacterial infections of the skin, respiratory tract, urinary tract, and bone.
Indications
- Skin and soft tissue infections
- Streptococcal pharyngitis
- Urinary tract infections
- Bone infections
Contraindications
- Hypersensitivity to cephalosporins
- History of severe penicillin allergy (caution)
Classification
Mechanism of Action
Binds penicillin-binding proteins and inhibits the final transpeptidation step of bacterial cell wall peptidoglycan synthesis, leading to cell lysis; it is bactericidal.
Pharmacodynamics
Time-dependent bactericidal activity against many gram-positive cocci and some gram-negative organisms, particularly useful for skin and soft tissue infections.
Pharmacokinetics
- Absorption
- Well absorbed orally and acid stable.
- Distribution
- Distributes into most tissues; relatively low protein binding.
- Metabolism
- Not significantly metabolized.
- Excretion
- Excreted largely unchanged in urine via renal tubular secretion.
- Half-life
- Approximately 1 hour
- Bioavailability
- Approximately 90%
- Protein Binding
- Approximately 10-15%
Dosage
Typical dosage: 250-500 mg every 6-12 hours
Available Forms
- Capsule
- Tablet
- Oral suspension
Side Effects
Common
- Diarrhea
- Nausea
- Abdominal pain
- Rash
Serious
- Anaphylaxis
- Clostridioides difficile colitis
Rare
- Stevens-Johnson syndrome
- Interstitial nephritis
Drug Interactions
Cephalexin may increase metformin plasma levels by competing for renal tubular secretion.
Reduces renal excretion of cephalexin, raising and prolonging its serum concentration.
Warnings
Pregnancy
Category B
Toxicity
Generally low toxicity; overdose may cause nausea, vomiting, and diarrhea.
Overdose
Provide supportive care and hydration; hemodialysis may help remove the drug in severe renal impairment.
References
Looking for patient-friendly information? Visit RemedyDoor for easy-to-read guides about this medication.