What is the recommended dosing for doxycycline (tetracycline antibiotic)?

Doxycycline Dosing Guidelines

The standard dosing regimen for doxycycline is 100 mg twice daily for most infections, with a loading dose of 200 mg on the first day recommended for many indications. 1, 2

General Dosing Principles

• Adults:

  • Initial dose: 200 mg on first day (100 mg every 12 hours)
  • Maintenance dose: 100 mg daily or 100 mg every 12 hours for more severe infections 1

• Children >8 years weighing <100 lbs (45 kg):

  • Initial dose: 2 mg/lb body weight divided into two doses on first day
  • Maintenance dose: 1 mg/lb body weight daily (single dose or divided) 1
  • For severe infections: Up to 2 mg/lb body weight may be used 1

• Children >8 years weighing >100 lbs: Use adult dosing 1

Specific Infection Dosing

Bacterial Infections

• Respiratory tract infections: 200 mg on first day, then 100 mg daily 3
• Urinary tract infections (chronic/severe): 100 mg every 12 hours 1
• Skin and soft tissue infections (MRSA): 100 mg twice daily for 5-10 days 2

Sexually Transmitted Infections

• Chlamydia/Nongonococcal urethritis: 100 mg twice daily for 7 days 2, 1, 4
• Uncomplicated gonococcal infections: 100 mg twice daily for 7 days 1
• STI post-exposure prophylaxis (doxy PEP): 200 mg as single dose within 72 hours of sexual exposure 5, 2

Tick-Borne Diseases

• Rocky Mountain Spotted Fever/Ehrlichiosis: 100 mg twice daily for at least 3 days after fever subsides (minimum 5-7 days) 5
• Anaplasmosis: 100 mg twice daily for 10 days 5, 2
• Lyme disease: 100 mg twice daily for 10-21 days 2
• Lyme disease prophylaxis: 200 mg single dose 2

Other Infections

• Malaria prophylaxis: 100 mg daily, beginning 1-2 days before travel and continuing for 4 weeks after leaving malarious area 1
• Inhalational anthrax (post-exposure): 100 mg twice daily for 60 days 1
• Syphilis (early): 100 mg twice daily for 2 weeks 1
• Syphilis (>1 year duration): 100 mg twice daily for 4 weeks 1

Administration Guidelines

• Take with adequate fluid to reduce risk of esophageal irritation 2, 1
• Take with food if gastric irritation occurs 2
• Remain upright for 30-60 minutes after taking to prevent esophageal irritation 2, 1
• Avoid taking within 2 hours of antacids, iron, calcium, magnesium supplements, or dairy products 2

Special Considerations

• Pregnancy: Generally contraindicated but may be used for short periods before 6 months gestation for life-threatening infections 2
• Children <8 years: Avoid due to risk of dental staining and enamel hypoplasia 2
• Renal impairment: No dosage adjustment needed at usual recommended doses 1

Common Side Effects

• Gastrointestinal: nausea, vomiting, diarrhea, esophageal irritation
• Dermatologic: photosensitivity
• Other: vaginal yeast infections 2

Important Cautions

• Do not exceed 200 mg per 24 hours for doxy PEP 5
• For STI prophylaxis, take as soon as possible after exposure but within 72 hours 5
• Monitor for antimicrobial resistance with prolonged use 2
• For tickborne diseases, never delay treatment while awaiting laboratory confirmation 5