Doxycycline Dosing for Bacterial Infections
For most bacterial infections in adults, doxycycline is dosed at 200 mg on the first day (100 mg every 12 hours), followed by 100 mg daily maintenance dosing, with treatment duration typically 7-10 days depending on the specific infection. 1
Standard Adult Dosing
- Loading dose: 200 mg on day 1, administered as 100 mg every 12 hours 1
- Maintenance dose: 100 mg daily thereafter 1
- For severe infections (particularly chronic urinary tract infections), continue 100 mg every 12 hours throughout treatment 1
Pediatric Dosing (Children >8 Years)
- Day 1: 2 mg/lb (4.4 mg/kg) body weight divided into two doses 1
- Subsequent days: 1 mg/lb (2.2 mg/kg) body weight as single daily dose or divided into two doses 1
- For severe infections, increase to 2 mg/lb body weight 1
- Children >100 lbs: Use standard adult dosing 1
Infection-Specific Duration Guidelines
Skin and Soft Tissue Infections
- Duration: Approximately 7 days, depending on clinical response 2
- Dosing: 100 mg twice daily orally for both MSSA and MRSA 2, 3
Respiratory Tract Infections
- Duration: 5-10 days 1, 4, 5
- Clinical improvement typically occurs by days 3-5 5
- 88% of patients achieve good or very good response with this regimen 4
Sexually Transmitted Infections
Chlamydia/NGU: 100 mg twice daily for 7 days 1
Uncomplicated gonorrhea: 100 mg twice daily for 7 days 1
Early syphilis (penicillin-allergic patients): 100 mg twice daily for 2 weeks 1
Late syphilis (>1 year duration): 100 mg twice daily for 4 weeks 1
Epididymo-orchitis: 100 mg twice daily for at least 10 days 1
Tickborne Rickettsial Diseases
- Dosing: Adults 100 mg twice daily; children <100 lbs receive 2.2 mg/kg twice daily 2
- Duration: At least 3 days after fever subsides and until clinical improvement is evident 2, 6
- Minimum course: 5-7 days typically 2, 6
- Severe or complicated disease may require longer treatment 6
- For anaplasmosis, extend to 10 days if concurrent Lyme disease is suspected 2
Anthrax (Post-Exposure Prophylaxis)
- Adults: 100 mg twice daily for 60 days 1
- Children <100 lbs: 1 mg/lb (2.2 mg/kg) twice daily for 60 days 1
Malaria Prophylaxis
- Adults: 100 mg daily 1
- Children >8 years: 2 mg/kg daily (up to adult dose) 1
- Begin 1-2 days before travel; continue during travel and for 4 weeks after leaving malarious area 1
Critical Administration Considerations
- Administer with adequate fluids to reduce risk of esophageal irritation and ulceration 1
- May give with food or milk if gastric irritation occurs; absorption is not significantly affected 1
- Oral therapy is appropriate for early-stage disease in outpatients 2
- Intravenous therapy is indicated for severely ill hospitalized patients, particularly those who are vomiting or obtunded 2
Important Clinical Pitfalls
Do Not Delay Treatment
- For rickettsial diseases, initiate treatment immediately based on clinical suspicion without waiting for laboratory confirmation 2, 6
- Delay in treatment can lead to severe disease, long-term sequelae, or death 2
Pediatric Use
- Children <8 years: Generally contraindicated due to dental staining risk 3
- Exception: May be used for severe infections (e.g., rickettsial diseases) when benefits outweigh risks 2, 6
- The concern about dental staining should not prevent use in life-threatening infections with short-term therapy 6
Pregnancy
- Generally contraindicated during pregnancy; alternative agents should be considered 3
Photosensitivity
- Counsel patients to avoid sun exposure due to increased risk of photosensitivity reactions 3
Monitoring Treatment Response
- Streptococcal infections: Continue therapy for 10 days 1
- Rickettsial diseases: If fever persists beyond 48 hours of treatment, consider alternative diagnoses or resistant infection 6
- Outpatients require close follow-up to ensure appropriate response 6
Renal Impairment
- Usual recommended doses do not lead to excessive accumulation in patients with renal impairment 1