Duration of Cephalexin 500mg BID Treatment
For skin and soft tissue infections, cephalexin 500mg twice daily should be administered for 7 days, with treatment extended if clinical improvement is not evident within 5 days. 1
Standard Treatment Duration
- The typical treatment duration for uncomplicated skin infections is 7 days, depending on clinical response, as recommended by the Infectious Diseases Society of America 1
- If the infection has not improved within 5 days, treatment should be extended 1
Dosing Considerations for BID Regimen
- The FDA label indicates that for streptococcal pharyngitis, skin and skin structure infections, and uncomplicated cystitis in patients over 15 years of age, 500mg may be administered every 12 hours 2
- For cystitis specifically, therapy should be continued for 7 to 14 days 2
- The standard adult dose ranges from 1 to 4 grams daily in divided doses 2
Clinical Efficacy of BID Dosing
- Cephalexin 500mg twice daily has demonstrated clinical efficacy comparable to four-times-daily dosing in multiple studies 3, 4, 5
- In a study of 752 patients with respiratory or soft tissue infections, over 80% were cured or considerably improved after 5 days of treatment with cephalexin 500mg or 1g twice daily 5
- The twice-daily regimen showed a trend toward more rapid response with higher dosing (1g BID), though this did not reach statistical significance 5
Important Limitations and Pitfalls
- Cephalexin is NOT effective against MRSA; if MRSA is suspected or confirmed, alternative agents such as trimethoprim-sulfamethoxazole, doxycycline, or clindamycin must be used instead 1, 6
- Cephalexin has limited activity against Pasteurella multocida and anaerobes 1, 6
- For β-hemolytic streptococcal infections specifically, a therapeutic dosage should be administered for at least 10 days 2