Doxycycline Dosing for Bacterial Infections
The typical dosage of doxycycline for bacterial infections in adults is 100 mg twice daily, with an initial loading dose of 200 mg on the first day, followed by a maintenance dose of 100 mg/day for 5-7 days, depending on the specific infection being treated. 1
Standard Dosing Regimen
Adults
- Initial dose: 200 mg on first day (administered as 100 mg every 12 hours) 1
- Maintenance dose: 100 mg daily or 100 mg every 12 hours for more severe infections 1
- Duration: Typically 5-7 days, but varies by infection type 2, 1
Children (≥8 years of age)
- For children weighing ≤100 pounds (45 kg): 2 mg/lb (4.4 mg/kg) of body weight divided into two doses on the first day, followed by 1 mg/lb (2.2 mg/kg) daily as a single dose or divided into two doses 1
- For more severe infections: Up to 2 mg/lb (4.4 mg/kg) of body weight may be used 1
- For children weighing >100 pounds: Use adult dosing 1
Infection-Specific Dosing
Skin and Soft Tissue Infections
Respiratory Tract Infections
- 100 mg twice daily for adults 3
- Duration: 5-10 days 4, 3
- Clinical improvement typically seen by day 3-5 of treatment 3
Sexually Transmitted Infections
- Uncomplicated gonococcal infections: 100 mg twice daily for 7 days 1
- Alternative single-visit dose: 300 mg followed by another 300 mg one hour later 1
- Chlamydia infections: 100 mg twice daily for 7 days 1
- Nongonococcal urethritis: 100 mg twice daily for 7 days 1
Tickborne Diseases
- Rickettsial diseases: 100 mg twice daily for adults; 2.2 mg/kg twice daily for children <100 lbs 2
- Duration: At least 3 days after fever subsides with minimum treatment of 5-7 days 2
- Lyme disease: 100 mg twice daily for 10-21 days 5
Administration Guidelines
- Can be administered with food or milk if gastric irritation occurs 1
- Adequate fluid intake is recommended with capsule and tablet forms to reduce the risk of esophageal irritation 1
- The absorption of doxycycline is not markedly influenced by simultaneous ingestion of food or milk 1
Special Considerations
- Doxycycline is generally contraindicated during pregnancy 5
- Traditionally contraindicated in children <8 years due to potential for dental staining, though benefits may outweigh risks in severe infections 5, 6
- Patients should avoid sun exposure due to increased risk of photosensitivity reactions 5
- For patients with renal impairment, standard doses can generally be used as doxycycline does not accumulate significantly 1
Common Pitfalls and Caveats
- Delaying treatment can lead to more severe disease and complications; treatment should be initiated based on clinical suspicion without waiting for laboratory confirmation 6
- Exceeding the recommended dosage may result in an increased incidence of side effects 1
- Most common side effects are gastrointestinal and photosensitivity 5
- Treatment failure may occur with certain pathogens due to resistance, particularly with H. influenzae (approximately 1/3 of cases) 7
Doxycycline remains an effective and economical option for treating many bacterial infections, with studies showing comparable efficacy to newer antibiotics like fluoroquinolones for conditions such as community-acquired pneumonia 8.
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