Cephalexin Dosing for Otitis Externa in a 17kg Child
Cephalexin is NOT the appropriate antibiotic choice for otitis externa. The evidence provided addresses acute otitis media (middle ear infection) and other respiratory/skin infections, but otitis externa (outer ear canal infection) requires different management—typically topical antibiotic/steroid drops rather than oral cephalosporins 1.
Critical Clinical Distinction
Otitis externa (swimmer's ear) is an infection of the external auditory canal, most commonly caused by Pseudomonas aeruginosa and Staphylococcus aureus, and is primarily treated with topical therapy 1.
Acute otitis media (middle ear infection behind the tympanic membrane) is what the guidelines address with oral antibiotics like amoxicillin or cephalexin 1, 2.
If Systemic Therapy Is Truly Indicated
If there are specific circumstances requiring oral antibiotics for otitis externa (such as extension beyond the ear canal, immunocompromised state, or severe cellulitis), and cephalexin must be used despite not being first-line:
Standard Cephalexin Dosing for This Child
- Dose: 425-850 mg per day (25-50 mg/kg/day) divided into 3-4 doses 2
- Practical administration:
For Severe Infections
- Higher dose: Up to 75-100 mg/kg/day in 4 divided doses may be used 2, 3
- For this 17kg child: Up to 1,275-1,700 mg daily divided into 4 doses 2
Important Caveats
- Cephalexin has poor activity against Pseudomonas aeruginosa, the most common pathogen in otitis externa 4
- Topical fluoroquinolone drops (ciprofloxacin/dexamethasone) are the standard of care for uncomplicated otitis externa 1
- If systemic antibiotics are needed for complicated otitis externa with cellulitis, consider anti-pseudomonal coverage with oral fluoroquinolones (in appropriate age groups) or parenteral therapy 1
Duration of Therapy
- Standard course: 7-10 days if oral therapy is used 2, 4
- Clinical improvement should occur within 48-72 hours; if not, reassess diagnosis and consider alternative pathogens or treatment failure 1, 5
Recommendation: Verify the diagnosis is truly otitis externa and not otitis media, as this fundamentally changes antibiotic selection and route of administration.