What is the recommended dosing of Keflex (cephalexin) for a patient with acute otitis media, considering age, weight, and renal function?

Keflex (Cephalexin) is NOT Recommended for Acute Otitis Media

Cephalexin should not be used for acute otitis media because it is inactive against Haemophilus influenzae, one of the three most common bacterial pathogens causing this infection, resulting in treatment failure rates of approximately 50% for H. influenzae cases. 1, 2

Why Cephalexin Fails in Otitis Media

• First-generation cephalosporins like cephalexin lack adequate activity against H. influenzae, which accounts for 27-30% of acute otitis media cases in children 2, 3
• Clinical studies demonstrate that cephalexin at dosages of 50-100 mg/kg/day fails in 50% of otitis media infections caused by H. influenzae 1
• Even at higher doses (100 mg/kg/day), cephalexin showed persistent H. influenzae in 5 of 7 treatment failures 2

Recommended First-Line Treatment Instead

High-dose amoxicillin (80-90 mg/kg/day) is the gold standard initial treatment for acute otitis media due to its effectiveness against all three common bacterial pathogens (S. pneumoniae, H. influenzae, M. catarrhalis), safety profile, low cost, and narrow microbiologic spectrum. 4

Specific Dosing Algorithm:

• Standard cases: Amoxicillin 80-90 mg/kg/day in 2 divided doses for 5-10 days 4
• Recent amoxicillin use (within 30 days) OR concurrent purulent conjunctivitis: High-dose amoxicillin-clavulanate 90 mg/kg/day of amoxicillin with 6.4 mg/kg/day of clavulanate in 2 divided doses 5, 4

When Cephalosporins ARE Appropriate

If cephalosporins must be used due to penicillin allergy or treatment failure, use second or third-generation agents, not cephalexin:

For Non-Type I Penicillin Allergy (rash, not anaphylaxis):

• Cefdinir: 14 mg/kg/day once daily or in 2 divided doses for 10 days 5, 4
• Cefuroxime axetil: 30 mg/kg/day in 2 divided doses (maximum 500 mg per dose) for 10 days 5

For Treatment Failure After 48-72 Hours:

• Ceftriaxone: 50 mg/kg IM or IV once daily for 1-3 days 4, 6

Critical Clinical Pitfalls to Avoid

• Do not prescribe cephalexin for otitis media - it provides inadequate coverage and leads to preventable treatment failures 1, 2
• The cross-reactivity risk between penicillins and second/third-generation cephalosporins is negligible (approximately 0.1%), making cefdinir or cefuroxime safe alternatives for non-anaphylactic penicillin allergies 4
• For true Type I hypersensitivity reactions (anaphylaxis, angioedema), avoid all beta-lactams and use azithromycin 12 mg/kg once daily for 5 days or clarithromycin 7.5 mg/kg twice daily for 10 days instead 5, 4

Reassessment Protocol

• Reassess at 48-72 hours if no clinical improvement occurs 4, 6
• Switch to amoxicillin-clavulanate 90 mg/kg/day if initial therapy fails 4
• Consider tympanocentesis for culture-directed therapy if no improvement after 72 hours of appropriate antibiotic therapy 6