What is the recommended dosage and duration of doxycycline (tetracycline antibiotic) for an adult patient with uncomplicated ear and sinus infections?

Doxycycline Dosing for Adult Ear and Sinus Infections

For an adult with uncomplicated ear and sinus infections, doxycycline should be dosed at 100 mg once daily for 10 days. 1, 2

Standard Dosing Protocol

• The recommended regimen is 100 mg orally once daily for 10 days for adults with acute bacterial sinusitis 1, 2
• The FDA-approved dosing for respiratory infections specifies 200 mg on the first day (100 mg every 12 hours), followed by 100 mg daily as maintenance 3
• However, clinical guidelines consistently support the simpler 100 mg once daily regimen for the full 10-day course without a loading dose for sinusitis 1, 2

Treatment Duration and Monitoring

• Complete the full 10-day course even if symptoms improve earlier to ensure complete bacterial eradication and prevent relapse 1, 2
• Evaluate clinical response at 3-5 days: if symptoms are improving, continue the full 10-day course 1, 2
• If no improvement or worsening occurs at 72 hours, switch to alternative therapy such as high-dose amoxicillin-clavulanate (4 g/250 mg per day) or a respiratory fluoroquinolone 1, 2
• Treatment should continue until the patient has been symptom-free for approximately 7 days, which typically aligns with the 10-14 day total course 1, 2

Position in Treatment Algorithm

Doxycycline is NOT a first-line agent for sinus infections but serves as an appropriate alternative in specific situations 1, 2:

• Use doxycycline for patients with β-lactam (penicillin) allergies who cannot receive amoxicillin-based therapy 1, 2
• Appropriate for mild disease in patients without recent antibiotic exposure (within previous 4-6 weeks) 1
• Predicted clinical efficacy is 77-81%, which is lower than amoxicillin-clavulanate (90-92%) or respiratory fluoroquinolones (90-92%) 1, 4

Critical Pitfalls to Avoid

• Stopping antibiotics prematurely when symptoms improve leads to incomplete eradication with a 20% recurrence rate 2
• Do not use doxycycline for viral upper respiratory infections—antibiotics are inappropriate for viral illness and contribute to resistance 2, 5
• Failing to reassess at 3-5 days delays necessary antibiotic switches, with a 15% failure rate in non-responders 2
• Bacteriologic failure rates of 20-25% are possible with doxycycline, particularly against resistant Streptococcus pneumoniae and Haemophilus influenzae 1

Administration Considerations

• Administer with adequate fluid to reduce risk of esophageal irritation and ulceration 3
• If gastric irritation occurs, give with food or milk—absorption is not significantly affected 3
• The therapeutic serum activity persists for 24 hours following the recommended dose 3

Preferred First-Line Alternatives

If the patient can tolerate β-lactams, strongly consider these more effective options instead:

• Amoxicillin-clavulanate 500 mg three times daily or 875 mg twice daily for 5-7 days (90-92% efficacy) 5, 4
• High-dose amoxicillin 1.5-4 g/day for patients without recent antibiotic use (83-88% efficacy) 1, 4
• These agents provide superior coverage against the most common pathogens: Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis 1

When to Switch Therapy

If doxycycline fails at 72 hours, switch based on initial coverage limitations:

• Change to high-dose amoxicillin-clavulanate (4 g/250 mg per day) for broader gram-positive and gram-negative coverage 1, 2
• Consider respiratory fluoroquinolones (levofloxacin, moxifloxacin) for moderate disease or treatment failures 1
• Alternative: ceftriaxone 1 g IM/IV daily for 5 days for severe cases 1

Special Populations

• Avoid in children under 8 years due to permanent dental staining risk 2, 4
• Avoid in pregnancy unless benefits clearly outweigh risks 2, 4
• For children ≥8 years: 4 mg/kg per day in 2 divided doses (maximum 100 mg per dose) for 10 days 2, 4