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

Doxycycline Dosage and Treatment Duration for Bacterial Infections

For most bacterial infections, doxycycline should be administered at 100 mg twice daily for 7-10 days, with specific durations tailored to the type of infection. 1, 2

Standard Dosing Regimen

• Adults:
  • Initial dose: 200 mg on first day (100 mg every 12 hours)
  • Maintenance dose: 100 mg twice daily 1
• Children >8 years and <100 lbs:
  • Initial dose: 2 mg/lb divided into two doses on first day
  • Maintenance dose: 1 mg/lb daily as single dose or divided 1

Treatment Duration by Infection Type

Respiratory Tract Infections

• Standard duration: 7-10 days 3
• Acute bronchitis/exacerbations of chronic bronchitis: 5-7 days 2, 3

Skin and Soft Tissue Infections

• MRSA skin infections: 5-10 days 2
• Cellulitis: 5-10 days 4

Sexually Transmitted Infections

• Chlamydia: 7 days 1, 2
• Nongonococcal urethritis: 7 days 1, 2
• Uncomplicated gonococcal infections: 7 days 1
• Syphilis (early): 14 days 1
• Syphilis (>1 year duration): 28 days 1
• Acute epididymo-orchitis: At least 10 days 1

Tickborne Diseases

• Human Granulocytic Anaplasmosis (HGA): 10 days 4, 2
• Lyme disease: 10-21 days 4, 2
• Rocky Mountain Spotted Fever: At least 3 days after fever subsides, minimum 5-7 days 4

Special Considerations

Administration Guidelines

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

Contraindications and Precautions

• Pregnancy: Generally contraindicated 2
• Children <8 years: Not recommended due to risk of dental staining 2
• Severe liver dysfunction: Contraindicated 5

Common Side Effects

• Gastrointestinal symptoms (nausea, vomiting, diarrhea) 2, 6
• Photosensitivity reactions - advise patients to avoid sun exposure 2, 6

Treatment Efficacy

• Therapeutic success rate of approximately 80% for respiratory and urinary tract infections 5
• Eradication rates of 92-96% for chlamydial infections 7

Clinical Pearls

• For severe infections (particularly chronic UTIs), 100 mg every 12 hours is recommended throughout treatment 1
• When treating streptococcal infections, therapy should continue for 10 days to prevent sequelae 1
• Doxycycline is the drug of choice for infections caused by Rickettsia, Borrelia, and Ehrlichia 5
• Low-dose doxycycline (20 mg twice daily) may be effective for moderate acne 8

Remember that treatment duration may need to be extended in cases of severe infection, slow clinical response, or immunocompromised patients 2.