Yes, Keflex (cephalexin) can be used to treat group A streptococcal pharyngitis
Cephalexin is a recommended first-line alternative for treating strep throat, particularly in penicillin-allergic patients, and is explicitly endorsed by major guidelines with strong evidence. 1, 2
Guideline Recommendations
Both the IDSA 2012 guidelines and the AHA 2009 scientific statement list cephalexin as a strong, high-quality recommendation for GAS pharyngitis 1, 2. The standard dosing is:
- Children: 20 mg/kg/dose twice daily (maximum 500 mg/dose) for 10 days 1
- Adults: 500 mg twice daily for 10 days 3
When to Use Cephalexin
Cephalexin is appropriate in two clinical scenarios:
- Penicillin-allergic patients (without immediate/anaphylactic-type hypersensitivity) - this is the primary indication per guidelines 1, 2
- As an alternative to penicillin when preferred, though penicillin V or amoxicillin remain first-line choices 1
Important Caveats
Avoid cephalexin in patients with immediate-type (anaphylactic) penicillin allergy, as up to 10% of penicillin-allergic individuals are also allergic to cephalosporins 2. In these cases, use clindamycin or macrolides instead.
The FDA label confirms cephalexin is "generally effective in the eradication of streptococci from the nasopharynx," though it notes that penicillin remains "the usual drug of choice" and that data establishing efficacy in preventing rheumatic fever are limited 3.
Clinical Efficacy
Research demonstrates cephalexin performs comparably or slightly better than penicillin for bacterial eradication. Studies show bacteriologic failure rates of 7% with cephalexin versus 11% with penicillin 4, with cure rates of approximately 96-98% across multiple trials 5, 6, 7. Recent network meta-analysis data suggest cephalexin-containing regimens may provide earlier symptom improvement 8, 9.
The critical requirement is completing the full 10-day course, even after symptoms resolve, to ensure adequate bacterial eradication and prevent complications 3.