Intravenous Doxycycline Dosing
The standard IV doxycycline dose for adults is 200 mg on the first day (given as one or two infusions), followed by 100-200 mg daily depending on infection severity. 1
Adult Dosing
Standard Regimen
- Initial dose: 200 mg IV on day 1, administered in one or two infusions 1
- Maintenance dose: 100-200 mg IV daily, depending on severity of infection 1
- Infusion time: Minimum 1 hour for 100 mg of a 0.5 mg/mL solution; typically 1-4 hours total 1
Specific Infections
- Inhalational anthrax: 100 mg IV every 12 hours, transitioning to oral when appropriate, for a total of 60 days (IV and oral combined) 2, 1
- Primary/secondary syphilis: 300 mg IV daily for at least 10 days 1
- Community-acquired pneumonia: 100 mg IV every 12 hours 3
Pediatric Dosing
Severe or Life-Threatening Infections
- Children <45 kg: 2.2 mg/kg IV every 12 hours 1
- Children ≥45 kg: Use adult dosing (100 mg every 12 hours) 2, 4
Less Severe Disease (>8 years, <45 kg)
- Day 1: 4.4 mg/kg divided into two doses 1
- Maintenance: 2.2 mg/kg daily (single dose or divided twice daily) 1
Critical Administration Guidelines
Preparation and Infusion
- Reconstitute 100 mg vial with 10 mL Sterile Water for Injection to create 10 mg/mL solution 1
- Further dilute to 0.1-1 mg/mL in compatible IV solutions (normal saline, D5W, lactated Ringer's, etc.) 1
- Avoid rapid administration - thrombophlebitis risk with prolonged IV therapy 1
- Do NOT inject intramuscularly or subcutaneously 1
Transition to Oral Therapy
- Switch to oral as soon as clinically possible - parenteral therapy should not be prolonged 1
- Oral bioavailability is excellent (approximately 100%), making transition straightforward 5
- Continue therapy 24-48 hours after fever subsides and clinical improvement 1
Special Populations
Renal Impairment
- No dose adjustment required - doxycycline does not accumulate excessively in renal failure 1, 6
- Can be used in dialysis patients without modification 6
Geriatric Patients
- Standard adult dosing applies - tissue penetration similar to younger adults 6
Pregnancy
- Generally contraindicated, but may be used for life-threatening infections (e.g., inhalational anthrax) when benefits outweigh risks 2, 7
Important Clinical Caveats
- Age restriction: Traditionally avoided in children <8 years due to dental staining risk, though acceptable for severe/life-threatening infections when benefits outweigh risks 4, 1
- CNS penetration: Poor penetration makes doxycycline suboptimal for meningitis 2
- Photosensitivity: Warn patients about increased sun sensitivity 7
- Drug interactions: Separate from dairy products, antacids, and supplements containing calcium, iron, magnesium by at least 2 hours 4