Doxycycline Dosage and Treatment Duration Guidelines
The standard adult dosage for doxycycline is 100 mg twice daily (200 mg on the first day), with treatment duration varying from 7-21 days depending on the specific infection being treated. 1
Standard Adult Dosing
- Initial dose: 200 mg on first day (administered as 100 mg every 12 hours)
- Maintenance dose: 100 mg daily (can be given as single dose or divided into two doses)
- For severe infections: 100 mg every 12 hours is recommended
Infection-Specific Dosing and Duration
Sexually Transmitted Infections
- Chlamydia: 100 mg orally twice daily for 7 days 2
- Nongonococcal urethritis: 100 mg orally twice daily for 7 days 2, 1
- Uncomplicated gonococcal infections: 100 mg orally twice daily for 7 days 1
- Alternative single-visit dose: 300 mg followed by another 300 mg one hour later
- Syphilis (early): 100 mg orally twice daily for 2 weeks 1
- Syphilis (>1 year duration): 100 mg orally twice daily for 4 weeks 1
- Acute epididymo-orchitis: 100 mg orally twice daily for at least 10 days 1
Respiratory Infections
- Community-acquired pneumonia: 100 mg twice daily for 7-14 days 3
- Acute bronchitis: 200 mg on first day, followed by 100 mg daily for 5-7 days 4
Other Infections
- Lyme disease: 100 mg orally twice daily for 10-21 days 2, 5
- Lyme disease prophylaxis: 200 mg as a single dose 2
- Malaria prophylaxis: 100 mg daily, beginning 1-2 days before travel and continuing for 4 weeks after leaving malarious area 1
- Inhalational anthrax (post-exposure): 100 mg orally twice daily for 60 days 1
- MRSA skin infections: 100 mg orally twice daily for 5-10 days 2
Pediatric Dosing (Children >8 years)
- Children ≤100 pounds: 2 mg/lb divided into two doses on first day, then 1 mg/lb daily as single dose or divided doses 1
- Children >100 pounds: Use adult dosage 1
- Important note: Doxycycline is not recommended for children younger than 8 years due to risk of dental staining and enamel hypoplasia 6, 2
Administration Guidelines
- Take with adequate amounts of fluid to reduce risk of esophageal irritation 1
- Can be taken with food or milk if gastric irritation occurs 1
- Remain upright for at least 30 minutes after taking to prevent esophageal irritation 2
- Avoid taking within 2 hours of antacids, dairy products, or supplements containing calcium, magnesium, aluminum, or iron 2
Special Considerations
- Renal impairment: No dosage adjustment needed 1, 7
- Pregnancy: Generally contraindicated; use only for life-threatening infections where alternatives aren't available 2
- Severe infections: May require higher dosing (100 mg every 12 hours) 1
- Streptococcal infections: Continue therapy for 10 days 1
Monitoring and Follow-up
- For STI treatment, bacterial STI testing should be performed at baseline and every 3-6 months 6
- Monitor for common side effects: nausea, photosensitivity, diarrhea, esophageal irritation 2
- For doxycycline PEP (post-exposure prophylaxis) for STI prevention, the recommended dose is 200 mg within 72 hours after sexual exposure 6
Doxycycline's convenient twice-daily dosing, excellent absorption, and broad spectrum of activity make it a preferred tetracycline for most indications 7. Its long half-life (approximately 12 hours) allows for consistent therapeutic serum activity over 24 hours with the recommended dosing schedule 1.