Doxycycline Dosing Recommendations
For most adult infections, doxycycline is dosed at 100 mg twice daily, with the standard duration being 7-14 days depending on the specific infection being treated. 1
Standard Adult Dosing
The typical adult regimen is 200 mg on day 1 (given as 100 mg every 12 hours), followed by 100 mg daily as maintenance therapy. For more severe infections, particularly chronic urinary tract infections, continue 100 mg every 12 hours throughout treatment 1.
Disease-Specific Dosing for Adults:
- Acute Q fever: 100 mg twice daily for 14 days 2
- Lyme disease: 100 mg twice daily for 10-21 days (depending on manifestation) 3
- Human Granulocytic Anaplasmosis (HGA): 100 mg twice daily for 10 days 3
- Skin/soft tissue infections (MRSA/MSSA): 100 mg twice daily 4, 5
- Early syphilis (penicillin-allergic): 100 mg twice daily for 2 weeks 1
- Late syphilis (>1 year duration): 100 mg twice daily for 4 weeks 1
- Chlamydia (urethral/cervical/rectal): 100 mg twice daily for 7 days 1, 6
- Malaria prophylaxis: 100 mg once daily 1
- Anthrax post-exposure prophylaxis: 100 mg twice daily for 60 days 7, 1
- Doxycycline post-exposure prophylaxis (Doxy-PEP) for STIs: 200 mg as a single dose within 72 hours after condomless sex (maximum 200 mg per 24 hours) 8
Pediatric Dosing
For children ≥8 years old: 4 mg/kg/day divided into 2 doses (maximum 100 mg per dose) 3
For children weighing ≤100 lbs: 2 mg/lb divided into 2 doses on day 1, then 1 mg/lb daily (or divided into 2 doses) on subsequent days 1
For children >100 lbs: Use standard adult dosing 1
Important Pediatric Considerations:
- Children <8 years: Doxycycline is generally avoided due to risk of permanent tooth discoloration and enamel hypoplasia 9
- Exception for severe/life-threatening infections: For high-risk children <8 years (hospitalized, severe illness, immunocompromised, pre-existing heart valve disease), the full 14-day course at 2.2 mg/kg twice daily is justified despite tooth staining concerns 2
- Short courses (≤5 days) have not been shown to cause significant dental staining, so may be considered for mild illness in children <8 years 2
Special Populations
Pregnant Women:
Doxycycline should be avoided in pregnancy except when benefits clearly outweigh risks in life-threatening situations 3, 7. For Q fever in pregnancy, use trimethoprim/sulfamethoxazole 160/800 mg twice daily throughout pregnancy instead 2.
Chronic Q Fever/Endocarditis:
100 mg twice daily PLUS hydroxychloroquine 200 mg three times daily for ≥18 months 2
Anti-inflammatory Dosing (Rosacea):
40 mg once daily (30 mg immediate-release/10 mg delayed-release formulation) provides sub-antimicrobial anti-inflammatory effects 9, 10, 11, 12
Administration Pearls
- Take with a full glass of water while sitting or standing to reduce esophagitis/esophageal ulceration risk 9, 1
- May take with food or milk if gastric irritation occurs; absorption is not significantly affected 1
- Avoid dairy products within 2 hours (before or after) when treating Q fever 2
- Avoid sun exposure due to photosensitivity risk 9
Key Monitoring
Routine drug level monitoring is not required 9. For prolonged therapy, monitor CBC, renal function, and liver function tests intermittently 9.