What is the dosage and treatment regimen for doxycycline?

Doxycycline Dosage and Treatment Regimen

The standard dosage for doxycycline is 100 mg orally twice daily for 7 days for most common infections, with a loading dose of 200 mg on the first day (100 mg twice daily) recommended for more rapid therapeutic effect. 1

Standard Dosing Regimens

Adult Dosing

• Initial dose: 200 mg on first day (100 mg every 12 hours)
• Maintenance dose: 100 mg daily, either as single dose or divided into two doses 1
• For more severe infections: 100 mg every 12 hours is recommended 1

Pediatric Dosing (children >8 years)

• Children ≤100 pounds: 2 mg/lb divided into two doses on first day, then 1 mg/lb daily
• Children >100 pounds: Use adult dosing 1
• Note: Doxycycline should be avoided in children under 8 years due to risk of dental staining 2

Infection-Specific Dosing

Sexually Transmitted Infections

• Chlamydia/Nongonococcal urethritis: 100 mg orally twice daily for 7 days 3, 2
• Uncomplicated gonococcal infections: 100 mg orally twice daily for 7 days 1
  • Alternative: 300 mg stat followed by 300 mg one hour later (single visit) 1
• Epididymo-orchitis: 100 mg orally twice daily for at least 10 days 1

Other Common Infections

• Lyme disease: 100 mg orally twice daily for 10-21 days 2, 1
• Malaria prophylaxis: 100 mg daily for adults 1
• Inhalational anthrax (post-exposure): 100 mg orally twice daily for 60 days 1
• Human Granulocytic Anaplasmosis: 100 mg orally twice daily for 10 days 2
• MRSA skin infections: 100 mg orally twice daily for 5-10 days 2

Administration Guidelines

• Take with adequate fluid to reduce risk of esophageal irritation 2
• May be taken with food or milk if gastric irritation occurs 1
• Avoid administration within 2 hours of antacids, iron, calcium, magnesium supplements, or dairy products 2
• Patient should remain upright for 30 minutes after taking doxycycline 2

Treatment Duration Considerations

• Standard duration for most infections is 7 days 3, 2
• Extended durations are necessary for:
  • Syphilis (early): 100 mg twice daily for 2 weeks 1
  • Syphilis (>1 year duration): 100 mg twice daily for 4 weeks 1
  • Lyme disease: 10-21 days 2, 4
  • Anthrax: 60 days 1

Clinical Pearls and Pitfalls

• Therapeutic levels: Plasma concentrations should be maintained above 1 μg/ml for optimal efficacy; some patients may require higher doses to achieve this 5
• Treatment failure: Patients should return for evaluation if symptoms persist or recur after completing therapy 3
• Sexual abstinence: Patients with STIs should abstain from sexual intercourse until 7 days after therapy is initiated and symptoms have resolved 3
• Partner treatment: For STIs, refer all sexual partners from the preceding 60 days for evaluation and treatment 3
• Recurrent urethritis: Consider tetracycline-resistant U. urealyticum in cases of recurrent urethritis after doxycycline treatment 3

Special Populations

• Pregnancy: Generally contraindicated, but may be used for short periods before 6 months of gestation for life-threatening infections 2
• Renal impairment: No dosage adjustment needed at usual recommended doses 1

Doxycycline has shown excellent efficacy across various infection types with minimal side effects when administered properly, making it a valuable broad-spectrum antibiotic option 6, 7.