Does Keflex (Cephalexin) treat strep throat or otitis media?

Cephalexin for Strep Throat and Otitis Media

Cephalexin is effective for strep throat but is not recommended as first-line therapy for otitis media due to limited efficacy against Haemophilus influenzae, which is a common causative pathogen in ear infections.

Strep Throat Treatment

Cephalexin is an appropriate treatment option for strep throat (group A streptococcal pharyngitis), particularly as a second-line agent. The World Health Organization's Expert Committee recommends:

• First-line therapy: Amoxicillin or phenoxymethylpenicillin 1
• Second-line therapy: Cephalexin or clarithromycin 1

Cephalexin is particularly valuable in strep throat treatment because:

• It demonstrates a lower rate of clinical relapse compared to penicillin (OR 0.55; 95% CI 0.31-0.99) 1
• It provides good tolerability and has a relatively narrow spectrum of activity 1
• The FDA-approved indication includes "respiratory tract infections caused by Streptococcus pneumoniae and Streptococcus pyogenes" 2

Dosing for Strep Throat

• Adults: 500 mg every 12 hours 2
• Children: 25-50 mg/kg/day in divided doses 2
• Treatment should continue for at least 10 days to prevent rheumatic fever 2

Otitis Media Treatment

Cephalexin is not recommended as first-line therapy for otitis media due to significant limitations:

• First-line therapy: Amoxicillin 1
• Second-line therapy: Amoxicillin-clavulanic acid 1

The limitations of cephalexin for otitis media include:

• Poor efficacy against Haemophilus influenzae, with treatment failure rates of approximately 50% even when the isolate appears sensitive in vitro 3
• In a comparative study, 50% of children with H. influenzae otitis media treated with cephalexin had poor responses, while none receiving ampicillin had poor responses (P<0.05) 3

While the FDA label includes otitis media as an indication 2, more recent evidence and guidelines do not support its use as a first-line agent due to these efficacy concerns.

Key Considerations for Clinical Decision-Making

When to Use Cephalexin:

1. For strep throat:

   • In penicillin-allergic patients (except those with immediate hypersensitivity reactions) 1
   • When first-line agents have failed
   • When compliance with twice-daily dosing is preferred over four-times-daily regimens

2. For otitis media:

   • Only when the causative organism is known to be susceptible (e.g., Staphylococcus aureus resistant to penicillin) 3
   • Not recommended empirically due to high failure rates with H. influenzae

Common Pitfalls to Avoid:

• Do not use cephalexin empirically for otitis media when H. influenzae is a likely pathogen
• Do not use in patients with immediate hypersensitivity reactions to penicillins 4
• Avoid using cephalexin for otitis media in children under 2 years, where H. influenzae is more common

Conclusion

For strep throat, cephalexin is an effective second-line agent with good clinical outcomes. For otitis media, cephalexin should not be used as empiric therapy due to poor efficacy against H. influenzae, a common causative pathogen. Amoxicillin remains the first-line treatment for otitis media, with amoxicillin-clavulanic acid as the recommended second-line option.