What is the recommended dosage of Cefalexin (Cephalexin) for treating bacterial infections?

Recommended Dosage of Cefalexin (Cephalexin) for Bacterial Infections

For adults, the recommended dosage of cephalexin is 250-500 mg every 6 hours or 500 mg every 12 hours, with a total daily dose ranging from 1-4 g depending on infection severity. 1

Adult Dosing

Standard Dosing:

• Mild to moderate infections: 250 mg every 6 hours (1 g daily) 1
• Severe infections: 500 mg every 6 hours (2 g daily) 1
• Alternative regimen: 500 mg every 12 hours for:
  • Streptococcal pharyngitis
  • Skin and skin structure infections
  • Uncomplicated cystitis in patients over 15 years 1

Specific Conditions:

• Skin and soft tissue infections: 500 mg four times daily or 500 mg twice daily 2, 3
• Urinary tract infections: 500 mg every 12 hours for 7-14 days 1, 4

Pediatric Dosing

• Standard pediatric dose: 25-50 mg/kg/day divided into 4 doses 1
• Streptococcal pharyngitis and skin infections: Total daily dose may be divided and administered every 12 hours 1
• Otitis media: 75-100 mg/kg/day in 4 divided doses 1
• β-hemolytic streptococcal infections: Treatment should continue for at least 10 days 1

Dosing Based on Weight (Suspension)

For 125 mg/5 mL suspension:

• 10 kg: 1/2 to 1 tsp four times daily or 1-2 tsp twice daily
• 20 kg: 1 to 2 tsp four times daily or 2-4 tsp twice daily
• 40 kg: 2 to 4 tsp four times daily or 4-8 tsp twice daily 1

For 250 mg/5 mL suspension:

• 10 kg: 1/4 to 1/2 tsp four times daily or 1/2-1 tsp twice daily
• 20 kg: 1/2 to 1 tsp four times daily or 1-2 tsp twice daily
• 40 kg: 1 to 2 tsp four times daily or 2-4 tsp twice daily 1

Special Considerations

Renal Impairment

• Patients with creatinine clearance <30 mL/min require dose reduction proportional to the reduced renal function 5
• Dose adjustment can be based on creatinine clearance or serum creatinine levels 5

Duration of Therapy

• Standard infections: 7-10 days
• Streptococcal infections: Minimum 10 days 1
• Urinary tract infections: 7-14 days 1

Clinical Pearls

• Cephalexin is not absorbed from the stomach but is rapidly absorbed in the upper intestine 5
• Twice-daily dosing (500 mg or 1 g) has shown similar efficacy to four-times-daily dosing in respiratory and soft tissue infections 3
• For urinary tract infections, cephalexin achieves high urinary concentrations (500-1000 μg/mL) following 250-500 mg oral doses 5
• Children may require higher doses per kilogram than adults due to greater body water turnover 5
• Cephalexin should be considered as a fluoroquinolone-sparing alternative for uncomplicated lower urinary tract infections 6

Common Pitfalls to Avoid

• Exceeding 4 g daily dose (consider parenteral cephalosporins if higher doses are required) 1
• Inadequate duration of therapy for streptococcal infections (should be at least 10 days) 1
• Failure to adjust dosing in patients with significant renal impairment 5
• Not considering local resistance patterns when prescribing for empiric therapy 7