Cephalexin Dosing for Streptococcal Pharyngitis and Uncomplicated Skin Infections
For streptococcal pharyngitis, cephalexin should be dosed at 500 mg orally twice daily for 10 days in adults, and for uncomplicated skin infections, 500 mg orally four times daily for 7-10 days is recommended. 1
Dosing for Adults
Streptococcal Pharyngitis
- Adult dose: 500 mg orally twice daily for 10 days 1
- Alternative dosing: 250 mg orally four times daily for 10 days 1
Uncomplicated Skin Infections
- Adult dose: 500 mg orally four times daily for 7-10 days 1
- Alternative dosing: 500 mg orally every 6 hours 2, 1
Dosing for Children
Streptococcal Pharyngitis
- Pediatric dose: 25-50 mg/kg/day divided in two doses (every 12 hours) for 10 days 1
- A full 10-day course is essential for complete eradication of streptococcal pharyngitis to prevent acute rheumatic fever 3
Uncomplicated Skin Infections
- Pediatric dose: 25-50 mg/kg/day divided in four doses (every 6 hours) for 7-10 days 1
- For severe infections, the dosage may be doubled 1
Weight-Based Dosing Chart for Suspension
For twice daily (BID) dosing:
| Weight | 125 mg/5 mL | 250 mg/5 mL |
|---|---|---|
| 10 kg | 1-2 tsp BID | 1/2-1 tsp BID |
| 20 kg | 2-4 tsp BID | 1-2 tsp BID |
| 40 kg | 4-8 tsp BID | 2-4 tsp BID |
For four times daily (QID) dosing:
| Weight | 125 mg/5 mL | 250 mg/5 mL |
|---|---|---|
| 10 kg | 1/2-1 tsp QID | 1/4-1/2 tsp QID |
| 20 kg | 1-2 tsp QID | 1/2-1 tsp QID |
| 40 kg | 2-4 tsp QID | 1-2 tsp QID |
Clinical Considerations
Efficacy
- Cephalexin has demonstrated equivalent efficacy when administered twice daily versus four times daily for streptococcal pharyngitis, making the twice-daily regimen a convenient option 4
- For skin infections, cephalexin has shown clinical cure rates of 91% in clinical trials 5
Duration of Therapy
- For streptococcal pharyngitis: A full 10-day course is mandatory to prevent complications like acute rheumatic fever 3
- For uncomplicated skin infections: 7-10 days is typically sufficient 1, 5
Alternative Antibiotics
- For penicillin-allergic patients (non-anaphylactic): Cephalexin remains a good option 3
- For patients with immediate hypersensitivity to penicillin: Consider clindamycin (300-450 mg three times daily) 3
Important Clinical Pearls
Drainage procedures: For skin infections with abscess formation, incision and drainage is crucial for successful treatment, sometimes more important than antibiotic choice 6
Monitoring: Assess for clinical improvement within 48-72 hours; most patients show improvement by this time 6
Storage of suspension: After reconstitution, cephalexin suspension should be refrigerated and may be kept for 14 days without significant loss of potency 1
Maximum daily dose: If daily doses greater than 4g are required, consider parenteral cephalosporins 1
Risk factors for treatment failure: Fever and age less than 1 year are associated with higher risk of treatment failure in skin infections 6
Cephalexin remains a reliable first-line option for both streptococcal pharyngitis and uncomplicated skin infections due to its efficacy, safety profile, and reasonable cost.