Cephalexin

General

• Type: 1st generation cephalosporin
• Dosage forms
  • Tabs: 250mg, 500mg, 750mg
  • Liquid: 125mg/5mL; 250mg/5mL
• Common Trade Names: Keflex

Adult Dosing

General

250-500mg PO q6h

Strep Pharyngitis

500mg PO q12h x 10 days

Uncomplicated UTI

500mg PO q12h x 7-14 days

Cellulitis and Other Skin Infections

500mg PO q12h

Pediatric Dosing

General

• 25-50 mg/kg/day PO divided q6-12h

Otitis Media

• 75-100 mg/kg/day PO divided q12h x 10 days
• Max: 4,000 mg/24h

Community Acquired Pneumonia

• 75-100 mg/kg/day PO divided q12h x 10 days

Contraindications

• Allergy to class/drug
  • See also Cephalosporin Cross-reactivity
• Caution advised with contraceptives

Adverse Drug Reactions

Serious

• Anaphylaxis
• Angioedema
• Erythema Multiforme
• Stevens-Johnson Syndrome
• Toxic Epidermal Necrolysis
• Clostridium difficile
• Neutropenia
• Thrombocytopenia
• Hemolytic anemia
• Hemorrhage
• Hepatitis
• Cholestatic jaundice
• Seizures

Common

• Diarrhea
• Nausea/vomiting
• Rash
• Headache
• Dizziness
• Transaminitis
• Eosinophilia

Pharmacology

• Half-life: 1h (~20hr ESRD)
• Metabolism: Minimal
• Excretion: Primarily urine (>90% unchanged)
• Mechanism of Action:
  • Bactericidal, inhibits cell wall

Pregnancy/Lactation

• Pregnancy: B
• Lactation: Safe

See Also

• Antibiotics (Main)
• Cephalosporin Cross-reactivity

Source

• Sanford 2010
• Epocrates