What is the recommended dosage and frequency of cephalexin (cephalexin) for a 17kg, 99cm tall child with otitis media?

Cephalexin Dosing for Otitis Media in a 17kg Child

For this 17kg child with otitis media, administer cephalexin 75-100 mg/kg/day divided into 4 doses (every 6 hours), which equals 320-425 mg per dose, or approximately 1.5-2 teaspoons (7.5-10 mL) of the 250 mg/5 mL suspension four times daily for 10 days. 1

Dosing Calculation and Rationale

The FDA label specifically states that for otitis media, clinical studies have demonstrated that 75-100 mg/kg/day in 4 divided doses is required. 1 This higher dosing is critical for adequate middle ear penetration and coverage of common otitis media pathogens.

Weight-Based Calculation for This Patient

• Total daily dose: 17 kg × 75-100 mg/kg = 1,275-1,700 mg/day 1
• Per dose (divided into 4 doses): 320-425 mg every 6 hours 1
• Using 250 mg/5 mL suspension: 6.4-8.5 mL per dose, practically rounded to 7.5-10 mL (1.5-2 teaspoons) four times daily 1

Frequency and Duration

• Administer every 6 hours (four times daily) to maintain adequate serum and tissue concentrations 1
• Continue treatment for at least 10 days to ensure complete eradication of β-hemolytic streptococcal infections and prevent complications 1
• Clinical studies demonstrate cephalexin is effective at 50-100 mg/kg/day for otitis media, though failures occur in approximately 50% of cases caused by Haemophilus influenzae 2

Critical Clinical Considerations

Important Limitations of Cephalexin for Otitis Media

Cephalexin is NOT first-line therapy for acute otitis media. The American Academy of Pediatrics recommends high-dose amoxicillin (80-90 mg/kg/day) as the preferred initial treatment due to superior coverage of Streptococcus pneumoniae and better efficacy 3. Cephalexin has documented failure rates of 50% against H. influenzae, a common otitis media pathogen 2.

When to Use Cephalexin

Cephalexin may be considered for:

• Non-anaphylactic penicillin allergy where second-generation cephalosporins are appropriate 4
• Skin and soft tissue infections where it demonstrates excellent efficacy at 25-50 mg/kg/day in 4 divided doses 5

Monitoring and Follow-Up

• Expect clinical improvement within 48-72 hours; if no improvement occurs, reevaluation is necessary and consider switching to amoxicillin-clavulanate or ceftriaxone 3
• Fever should resolve within 24-48 hours for most bacterial infections 4
• Complete the full 10-day course even if symptoms improve earlier to prevent treatment failure and resistance 4

Common Pitfalls to Avoid

• Underdosing: The standard 25-50 mg/kg/day dosing used for skin infections is insufficient for otitis media; the higher 75-100 mg/kg/day dose is essential 1
• Inadequate frequency: Administering only 2-3 times daily instead of 4 times daily results in subtherapeutic levels 1
• Using cephalexin as first-line: Consider amoxicillin 80-90 mg/kg/day as preferred initial therapy unless contraindicated 3
• Failure to reassess: If the patient received antibiotics within the past 30 days or shows no improvement by 48-72 hours, switch to amoxicillin-clavulanate (90 mg/kg/day of amoxicillin component) for β-lactamase-producing organism coverage 3