Doxycycline Pediatric Dosing
For pediatric patients, doxycycline should be dosed at 2.2 mg/kg every 12 hours (maximum 100 mg per dose) for children under 100 pounds, and standard adult dosing (100 mg every 12 hours) for children over 100 pounds, regardless of age when treating serious infections. 1, 2
Weight-Based Dosing Algorithm
Children Under 100 Pounds (< 45 kg)
- Standard dose: 2.2 mg/kg every 12 hours, not to exceed 100 mg per dose 1, 2
- Alternative calculation: 2 mg/lb divided into 2 doses on day 1, then 1 mg/lb daily (as single dose or divided) on subsequent days 1
- This dosing applies to all children under 100 pounds, including those under 8 years of age when benefits outweigh risks 1
Children Over 100 Pounds (> 45 kg)
- Loading dose: 200 mg on day 1 (administered as 100 mg every 12 hours) 1, 2
- Maintenance dose: 100 mg daily, which can be given as a single dose or divided into 100 mg every 12 hours depending on infection severity 1, 2
Age Considerations: The Paradigm Shift
The historical contraindication for children under 8 years has been revised by the American Academy of Pediatrics based on compelling safety data. 1, 3
Use in Children Under 8 Years
- Short-term use (≤21 days) does not cause permanent tooth staining or enamel hypoplasia 1, 3, 4
- A prospective study of 38 children found zero cases of tetracycline-like staining after permanent teeth erupted following doxycycline exposure 4
- The key distinction: doxycycline differs from older tetracyclines (tetracycline, minocycline, oxytetracycline) which DO cause permanent staining and remain contraindicated 3
Approved Indications for All Ages (Including < 8 Years)
- Life-threatening tickborne rickettsial diseases: Rocky Mountain Spotted Fever, ehrlichiosis, anaplasmosis 1, 3
- Anthrax exposure: Both treatment and post-exposure prophylaxis (60-day course) 1, 3
- Other serious infections when alternative antibiotics are inadequate 3
When to Avoid in Young Children
- Prolonged or repeated courses should be avoided due to cumulative exposure risk 3
- Non-serious infections with adequate alternative antibiotics 3
Condition-Specific Dosing Durations
Tickborne Rickettsial Diseases
- Minimum 5-7 days total, continuing at least 3 days after fever resolves 1
Anthrax Post-Exposure Prophylaxis
- 100 mg twice daily for 60 days (children > 100 pounds) 1
- 2.2 mg/kg every 12 hours for 60 days (children < 100 pounds) 1
MRSA Skin Infections
- 100 mg twice daily for 7-14 days based on clinical response 2
Osteomyelitis (from MRSA guidelines)
- Greater than 6 weeks duration 5
- Note: The Taiwan MRSA guidelines state doxycycline is not recommended for children under 8 years, but this conflicts with more recent American Academy of Pediatrics recommendations that prioritize life-threatening infections 5, 1
Critical Administration Guidelines
Esophagitis Prevention
Drug Interactions
- Separate from dairy products, antacids, calcium, iron, magnesium, aluminum, or sodium bicarbonate by at least 2-3 hours 1, 3
- These substances significantly impair doxycycline absorption 3
Common Pitfalls to Avoid
Do not underdose young children: Pharmacokinetic studies demonstrate that clearance and volume of distribution (when allometrically scaled) do not differ between children 2-8 years and children >8 years, supporting the same mg/kg dosing across age groups 6
Do not confuse doxycycline with other tetracyclines: Only doxycycline has the updated safety profile for short-term use in young children 3, 7
Do not withhold doxycycline for serious infections in young children: Delaying appropriate treatment for Rocky Mountain Spotted Fever or other life-threatening infections carries far greater morbidity and mortality risk than theoretical tooth staining 3
Obesity does not require dose adjustment: Population pharmacokinetic modeling found obesity was not a significant covariate affecting doxycycline clearance or volume of distribution 6