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

Doxycycline Dosage and Treatment Duration for Bacterial Infections

The standard dosage of doxycycline for most bacterial infections in adults is 100 mg twice daily, with treatment durations varying from 7 to 60 days depending on the specific infection. 1

Standard Dosing Regimen

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 of age):

• 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)
• For severe infections: Up to 2 mg/lb body weight may be used
• For children >100 lbs: Use adult dosing 1

Important: Doxycycline is not recommended for children under 8 years due to risk of dental staining and enamel hypoplasia 2

Infection-Specific Dosing and Duration

Skin and Soft Tissue Infections

• MRSA/MSSA skin infections: 100 mg twice daily for 5-10 days 3
• Cutaneous anthrax: 100 mg twice daily for 7-10 days (mild cases); extend to 60 days if bioterrorism exposure suspected 3
• Bacillary angiomatosis: 100 mg twice daily for 4 weeks 3

Sexually Transmitted Infections

• Chlamydia: 100 mg twice daily for 7 days 2
• Nongonococcal urethritis: 100 mg twice daily for 7 days 2, 1
• Uncomplicated gonococcal infections: 100 mg twice daily for 7 days 1
• Mycoplasma genitalium: 100 mg twice daily for 7 days, potentially followed by other antibiotics based on resistance patterns 4
• Syphilis (early): 100 mg twice daily for 2 weeks (penicillin-allergic patients) 1
• Syphilis (>1 year duration): 100 mg twice daily for 4 weeks (penicillin-allergic patients) 1
• Epididymo-orchitis: 100 mg twice daily for at least 10 days 1

Respiratory Tract Infections

• Acute bronchitis/exacerbation of chronic bronchitis: 200 mg on first day, followed by 100 mg daily (200 mg daily may be continued in severe cases) 5
• Pneumonia: 100 mg twice daily for 7-21 days 3

Other Systemic Infections

• Tularemia (mild cases): 100 mg twice daily for 14 days 3
• Inhalational anthrax (post-exposure): 100 mg twice daily for 60 days 3, 1
• Malaria prophylaxis: 100 mg daily, starting 1-2 days before travel and continuing for 4 weeks after leaving malarious area 1
• Multidrug-resistant Gram-negative bacterial infections: 100 mg daily or twice daily, duration based on infection site and severity 6

Administration Guidelines

• Take with adequate amounts of fluid to reduce risk of esophageal irritation
• Can be taken with food or milk if gastric irritation occurs
• Remain upright for at least 30 minutes after taking to prevent esophageal irritation 1
• Avoid taking within 2 hours of antacids, dairy products, or supplements containing calcium, magnesium, iron, or aluminum 2

Special Considerations

• Renal impairment: Standard doses generally do not lead to excessive accumulation 1
• Pregnancy: Contraindicated; consider alternative antibiotics 2
• Photosensitivity: Advise patients to use sunscreen and protective clothing 2
• Long-term use: Sub-antimicrobial doses (20 mg twice daily) have been shown not to affect intestinal flora 7

Common Pitfalls to Avoid

1. Inadequate dosing: For severe infections, use 100 mg twice daily rather than once daily
2. Insufficient duration: Complete the full course to prevent relapse and resistance
3. Inappropriate use in children under 8: Can cause permanent tooth discoloration
4. Drug interactions: Avoid concurrent use with antacids, iron supplements, and certain other medications
5. Improper administration: Taking without adequate fluid or lying down after administration increases risk of esophageal ulceration

For optimal outcomes in terms of morbidity and mortality, ensure appropriate dosing, duration, and administration based on the specific infection being treated.