What is the dosage and treatment duration of doxycycline for infections?

Doxycycline Dosage and Treatment Duration for Infections

For most bacterial infections, doxycycline should be administered at 100 mg twice daily for 7-14 days, with the specific duration determined by the type of infection being treated. 1, 2

General Dosing Guidelines

• Standard adult dosage: 100 mg twice daily (oral or IV if unable to take oral medication) 1, 2
• Initial loading dose: 200 mg on first day (100 mg every 12 hours), followed by maintenance dose of 100 mg/day or 100 mg twice daily depending on infection severity 1
• Pediatric dosage (for children >8 years): 2-4 mg/kg/day divided into two doses (maximum 100 mg per dose) 2

Treatment Duration by Infection Type

Respiratory Tract Infections

• Acute bronchitis/pneumonia: 7-10 days 3
• Initial dosing: 200 mg on first day, followed by 100 mg daily (200 mg daily may be continued for severe cases) 3
• Clinical improvement typically occurs by day 3-5 of treatment 3

Tick-Borne Diseases

• Human Granulocytic Anaplasmosis (HGA): 100 mg twice daily for 10 days 2
• Lyme disease:
  • Early localized/disseminated: 100 mg twice daily for 10-21 days (10 days is sufficient for doxycycline) 2
  • For children ≥8 years: 4 mg/kg/day in 2 divided doses (maximum 100 mg per dose) 2

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, 4
• Lymphogranuloma venereum: 100 mg twice daily for 7 days (recent evidence shows this is effective, though traditional recommendations were for 21 days) 5
• Syphilis:
  • Early: 100 mg twice daily for 2 weeks 2, 1
  • Late (>1 year duration): 100 mg twice daily for 4 weeks 1

Skin and Soft Tissue Infections

• MSSA/MRSA infections: 100 mg twice daily for 7-14 days 2
• Acute epididymo-orchitis: 100 mg twice daily for at least 10 days 1

Special Considerations

• Administration: Take with a full glass of water to reduce risk of esophagitis and esophageal ulceration 2

• Food interactions: Can be taken with food or milk if gastric irritation occurs; absorption is not markedly influenced by simultaneous food intake 1

• Contraindications:

  • Children under 8 years (risk of permanent teeth discoloration and enamel hypoplasia) 2
  • Pregnancy and breastfeeding (relative contraindication) 2
  • History of hypersensitivity to tetracyclines 2

• Monitoring: Regular monitoring of complete blood count, liver function, and renal function is recommended for prolonged therapy 2

Common Pitfalls and Caveats

• Photosensitivity: Patients should avoid direct exposure to extensive sunlight or UV radiation 2
• Bacterial resistance: High-dose administration (100-200 mg/day) for extended periods may contribute to bacterial resistance; however, this is the necessary therapeutic dose for most infections 6
• Jarisch-Herxheimer reaction: Patients may experience a transient intensification of symptoms during the first 24 hours of therapy, particularly with spirochetal infections 2
• Alternative for children <8 years or pregnant women: Rifampin may be used for certain infections (such as HGA) when doxycycline is contraindicated 2

For optimal outcomes with minimal risk of resistance, complete the full prescribed course of doxycycline even if symptoms improve before completion 2, 1.