Doxycycline Dosing for Lyme Disease Based on Weight
For children weighing less than 100 pounds (45.4 kg), use weight-based dosing of doxycycline at 2.2 mg/kg twice daily. For individuals weighing 100 pounds or more, use the adult dose of 100 mg twice daily. 1
Dosing Guidelines by Weight
- For children weighing <100 pounds (45.4 kg): 2.2 mg/kg body weight per dose administered twice daily (orally or intravenously) 1
- For adults and children weighing ≥100 pounds (45.4 kg): 100 mg twice daily (orally or intravenously) 1
Age Considerations for Doxycycline Use
- Doxycycline is now recommended for Lyme disease treatment in all age groups, including children under 8 years of age, when indicated 2
- Previous concerns about dental staining in children under 8 years have been largely disproven with short courses of therapy 3, 4
- For children under 8 years with non-neurological Lyme disease, amoxicillin remains the preferred first-line treatment, with doxycycline as an alternative 1, 3
- For neurological Lyme disease manifestations, doxycycline is preferred regardless of age due to its excellent CNS penetration 1
Duration of Treatment
- For early localized or early disseminated Lyme disease with erythema migrans: 14 days (range 10-21 days) 1
- For neurological Lyme disease: 14-28 days 1
- For Lyme arthritis: 28 days 1
- Extending treatment beyond recommended durations has not been shown to enhance therapeutic efficacy 5
Administration Considerations
- Doxycycline should be taken with 8 ounces of fluid to reduce the risk of esophageal irritation 1
- Taking doxycycline with food can reduce gastrointestinal intolerance 1
- Patients should avoid sun exposure while taking doxycycline due to risk of photosensitivity 1
- Doxycycline has the advantage of also being effective for human granulocytic anaplasmosis (HGA), which may occur simultaneously with early Lyme disease 1
Monitoring and Potential Adverse Effects
- Most common adverse effects include gastrointestinal symptoms (nausea, vomiting, diarrhea) and photosensitivity 1
- Dental staining is rare with short courses of therapy, even in young children 3, 4
- Monitor for clinical response - fever and symptoms typically improve within 24-48 hours of initiating appropriate therapy 1
- Lack of response within 48 hours may indicate an alternative diagnosis or need for different treatment 1
Special Considerations
- Pregnant or lactating women should avoid doxycycline; use amoxicillin instead 1
- For patients with severe disease or inability to tolerate oral medications, intravenous administration may be necessary 1
- First-generation cephalosporins like cephalexin are ineffective for Lyme disease and should not be used 1
The transition from pediatric weight-based dosing to adult dosing at 100 pounds (45.4 kg) is clearly established in guidelines and represents the appropriate threshold for dosing changes in Lyme disease treatment 1.