Doxycycline Dosage and Treatment Regimens
The standard dosage of doxycycline for most infections in adults is 100 mg orally twice daily, with treatment duration varying from 7-21 days depending on the specific infection being treated. 1, 2
Standard Adult Dosing
- Initial dose: 200 mg on the first day (administered as 100 mg every 12 hours)
- Maintenance dose: 100 mg daily or 100 mg every 12 hours depending on infection severity 2
- Administration: Take with adequate fluid to reduce risk of esophageal irritation 2
- Food considerations: Can be taken with food or milk if gastric irritation occurs 2
Specific Infection Regimens
Sexually Transmitted Infections
- Chlamydia: 100 mg orally twice daily for 7 days 1
- Nongonococcal urethritis: 100 mg orally twice daily for 7 days 2
- Uncomplicated gonococcal infections: 100 mg orally twice daily for 7 days 2
- Alternative single-visit dose: 300 mg followed in one hour by another 300 mg 2
- Syphilis (early): 100 mg orally twice daily for 2 weeks (for penicillin-allergic patients) 2, 3
- Syphilis (>1 year duration): 100 mg orally twice daily for 4 weeks 2
Other Infections
- Pelvic Inflammatory Disease: 100 mg IV or orally every 12 hours, typically for 14 days total 3
- Respiratory tract infections: 200 mg on first day, then 100 mg daily 4
- Human Granulocytic Anaplasmosis: 100 mg orally twice daily for 10 days 1
- Lyme disease treatment: 100 mg orally twice daily for 10-21 days 1
- Lyme disease prophylaxis: 200 mg single dose 1
- Malaria prophylaxis: 100 mg daily, beginning 1-2 days before travel and continuing for 4 weeks after leaving malarious area 2
- Inhalational anthrax (post-exposure): 100 mg orally twice daily for 60 days 2
Pediatric Dosing
- Children >8 years and <100 lbs: 2 mg/lb divided into two doses on first day, then 1 mg/lb daily as single dose or divided doses 2
- Children >8 years and >100 lbs: Use adult dosing 2
- Children <8 years: Doxycycline is contraindicated due to risk of dental staining and enamel hypoplasia 1
Special Considerations
Treatment Duration
- Treatment duration varies by indication:
- Most bacterial infections: 7-14 days
- Syphilis: 2-4 weeks depending on stage
- Respiratory infections: typically 5-10 days
- Malaria prophylaxis: duration of travel plus 4 weeks after
Important Precautions
- Pregnancy: Generally contraindicated; use only for life-threatening infections when alternatives aren't available 1
- Alcohol consumption: May decrease half-life of doxycycline, potentially requiring twice-daily dosing in patients with chronic alcohol consumption 5
- Administration timing: Take with full glass of water and remain upright for at least 30 minutes afterward to prevent esophageal irritation 1
- Drug interactions: Avoid taking within 2 hours of antacids, dairy products, or supplements containing calcium, magnesium, aluminum, or iron 1
- Photosensitivity: Advise patients to use sunscreen and protective clothing 1
Monitoring
- For sexually transmitted infections, follow-up testing is recommended to ensure cure
- Monitor for side effects including nausea, vomiting, diarrhea, esophageal irritation, and photosensitivity 1
- For long-term use, monitor for potential development of antimicrobial resistance 1
Doxycycline is a versatile antibiotic with broad-spectrum coverage that makes it suitable for treating many different types of infections. The dosage regimen should be tailored to the specific infection being treated, with attention to patient factors such as age, weight, and comorbidities.