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

Doxycycline Dosage and Treatment Duration for Bacterial Infections

For most bacterial infections in adults, doxycycline should be administered at 100 mg twice daily, with an initial loading dose of 200 mg on the first day of treatment, followed by maintenance dosing that varies in duration based on the specific infection being treated. 1

Standard Adult Dosing

• Initial dose: 200 mg on first day (administered as 100 mg every 12 hours)
• Maintenance dose: 100 mg daily or 100 mg every 12 hours depending on infection severity
• Administration: Take with adequate fluid to reduce risk of esophageal irritation; can be taken with food if gastric irritation occurs 1

Infection-Specific Dosing and Duration

Respiratory Tract Infections

• Standard dosing: 100 mg twice daily
• Duration: 5-10 days for acute bronchitis; 7-14 days for pneumonia 2
• Severe infections: May continue 200 mg daily in severe cases 2

Sexually Transmitted Infections

• Uncomplicated gonococcal infections: 100 mg twice daily for 7 days 1
• Chlamydia trachomatis: 100 mg twice daily for 7 days 1
• Nongonococcal urethritis: 100 mg twice daily for 7 days 1
• 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

Skin and Soft Tissue Infections

• MRSA/MSSA skin infections: 100 mg twice daily for 5-10 days 3
• Duration: Treatment typically continues for 7 days, depending on clinical response 3

Genitourinary Infections

• Acute epididymo-orchitis (N. gonorrhoeae): 100 mg twice daily for at least 10 days 1
• Acute epididymo-orchitis (C. trachomatis): 100 mg twice daily for at least 10 days 1
• Urinary tract infections: 100 mg twice daily for 7-10 days 4

Severe/Chronic Infections

• Chronic urinary tract infections: 100 mg every 12 hours 1
• Prostatitis: 200 mg daily for 10 days 4

Special Situations

• Inhalational anthrax (post-exposure): 100 mg twice daily for 60 days 3, 1
• Malaria prophylaxis: 100 mg daily, beginning 1-2 days before travel and continuing for 4 weeks after leaving malarious area 1
• Tularemia (mild cases): 100 mg twice daily for 14 days 3
• Cutaneous bacillary angiomatosis: Standard doses for 4 weeks 3

Pediatric Dosing (>8 years of age)

• Initial dose: 2 mg/lb (4.4 mg/kg) of body weight divided into two doses on first day
• Maintenance dose: 1 mg/lb (2.2 mg/kg) of body weight given as single daily dose or divided into two doses
• Severe infections: Up to 2 mg/lb (4.4 mg/kg) of body weight may be used
• Children >100 lbs: Use adult dose 1

Important Considerations

Contraindications and Precautions

• Not recommended for children under 8 years due to risk of dental staining and enamel hypoplasia 3, 5
• Use with caution in pregnancy: Generally contraindicated but may be used for short periods (7-14 days) before 6 months gestation for life-threatening infections 5

Administration Tips

• Take with full glass of water
• Remain upright for at least 30 minutes after taking to prevent esophageal irritation
• Can be taken with food if gastric irritation occurs, though absorption is not markedly influenced by food 1

Monitoring

• Monitor for common side effects: nausea, vomiting, diarrhea, photosensitivity
• Long-term sub-antimicrobial dosing (20 mg twice daily) has been shown not to affect intestinal flora 6
• For prolonged therapy, monitor for development of resistant organisms 5

Treatment Success Indicators

• Clinical improvement typically occurs within 3-5 days for respiratory infections 2
• For STIs, follow-up testing may be required to confirm eradication

Doxycycline's broad spectrum of activity makes it valuable for treating various bacterial infections, including those caused by multidrug-resistant gram-negative bacteria, with clinical and microbiological improvement rates of over 80% reported in some studies 7.