What is the recommended dosage of cephalexin (cephalosporin) for treating bacterial otitis media?

Cephalexin Dosage for Bacterial Otitis Media

For bacterial otitis media, cephalexin should be administered at a dosage of 75-100 mg/kg/day in 4 divided doses for children, and 250-500 mg every 6 hours for adults. 1, 2

Pediatric Dosing

First-line recommendation:

• Dosage: 75-100 mg/kg/day divided into 4 doses 1
• Duration: 7-10 days (10 days for children under 2 years) 2
• Administration: Oral suspension or capsules depending on age

For a typical pediatric patient by weight:

• 10 kg (22 lb): 1/2 to 1 tsp of 125 mg/5 mL suspension four times daily 1
• 20 kg (44 lb): 1 to 2 tsp of 125 mg/5 mL suspension four times daily 1
• 40 kg (88 lb): 2 to 4 tsp of 125 mg/5 mL suspension four times daily 1

Clinical evidence:

Cephalexin has demonstrated effectiveness for otitis media at these dosages, with clinical studies showing that 75-100 mg/kg/day in 4 divided doses is specifically required for otitis media treatment 1. A study found that cephalexin was effective in treating 90 out of 97 children with otitis media at a dosage of 100 mg/kg/day 3.

Adult Dosing

First-line recommendation:

• Dosage: 250-500 mg every 6 hours 1
• Duration: 7-10 days
• Maximum daily dose: 4 g 1

Pathogen Coverage

Cephalexin is effective against most common otitis media pathogens:

• Streptococcus pneumoniae
• Group A beta-hemolytic streptococci

However, cephalexin has limitations against:

• Haemophilus influenzae (approximately 50% failure rate) 4

Alternative Antibiotics When Cephalexin Is Not Appropriate

If cephalexin is not suitable due to suspected H. influenzae infection or other factors:

1. Amoxicillin: 90 mg/kg/day divided twice daily (first-line for children under 2 years) 2
2. Amoxicillin-clavulanate: 90 mg/kg/day of amoxicillin with 6.4 mg/kg/day of clavulanate 2
3. Other cephalosporins:
   • Cefdinir: 14 mg/kg/day divided twice daily 2
   • Cefpodoxime: 8-10 mg/kg/day divided twice daily 5
   • Cefuroxime: 30 mg/kg/day divided twice daily 2
4. For penicillin/cephalosporin allergies:
   • Clindamycin: 30-40 mg/kg/day in 3 divided doses 2

Monitoring and Follow-up

• Assess clinical response within 48-72 hours
• If symptoms worsen or fail to improve within this timeframe, consider:
  • Reassessing diagnosis
  • Switching to an alternative antibiotic with better H. influenzae coverage
  • Referral to ENT specialist for severe cases or multiple treatment failures 2

Important Clinical Considerations

1. Pain management: Acetaminophen or ibuprofen should be provided regardless of antibiotic choice 2

2. Treatment failure: Often due to H. influenzae infection, as cephalexin has limited efficacy against this pathogen 4

3. Post-treatment follow-up: Be aware that 60-70% of children will have middle ear effusion at 2 weeks after successful treatment, which represents otitis media with effusion (OME), not treatment failure 2

4. Complications: Monitor for rare complications such as mastoiditis, which may require more aggressive intervention 2

By following these dosing recommendations and considering the pathogen coverage limitations of cephalexin, clinicians can effectively treat most cases of bacterial otitis media while being prepared to adjust therapy when necessary.