Cefixime Dosing for 100kg 15-Year-Old
For a 15-year-old weighing 100 kg, administer cefixime 400 mg once daily (the standard adult dose), as children weighing more than 45 kg or older than 12 years should receive the adult dose. 1
Dosing Rationale
The FDA-approved dosing for cefixime clearly establishes that:
- Pediatric patients (6 months or older): Standard dose is 8 mg/kg/day
- Transition to adult dosing: Children weighing >45 kg OR older than 12 years receive the adult dose of 400 mg daily 1
Since your patient meets BOTH criteria (>45 kg AND >12 years), the adult dose definitively applies.
Administration Options
The 400 mg daily dose can be given as:
- Single daily dose: 400 mg once daily (preferred for compliance)
- Divided dosing: 200 mg twice daily (if better tolerated)
The capsule may be administered without regard to food 1
Important Clinical Considerations
Duration of therapy depends on indication:
- Most respiratory tract infections: 7-10 days
- Streptococcus pyogenes infections (pharyngitis/tonsillitis): Minimum 10 days 1
- Uncomplicated gonorrhea: Single 400 mg dose 1
Renal function: With normal renal function (CrCl ≥60 mL/min), no dose adjustment is needed. If renal impairment exists, dose reduction may be necessary 1
Common pitfall: Do NOT calculate 8 mg/kg for this patient (which would yield 800 mg/day). This would exceed the maximum adult dose and is not supported by the labeling. The FDA explicitly caps dosing at the adult dose for patients in this age/weight category 1
Safety profile: Cefixime demonstrates excellent tolerability in adolescents, with adverse events occurring in approximately 1-2% of patients, predominantly mild gastrointestinal effects 2