What is the dosage and administration of doxycycline for bacterial infections?

Dosage and Administration of Doxycycline for Bacterial Infections

For adults with bacterial infections, doxycycline should be administered at 100 mg twice daily (200 mg/day), with a loading dose of 200 mg (100 mg every 12 hours) on the first day of treatment. 1

Standard Dosing Regimens

Adults

• Initial dose: 200 mg on day 1 (administered as 100 mg every 12 hours)
• Maintenance dose: 100 mg daily as a single dose or 100 mg every 12 hours for more severe infections 1
• Duration: Typically 7-14 days for most bacterial skin and soft tissue infections 2

Children (>8 years of age)

• Initial dose: 2 mg/lb (4.4 mg/kg) of body weight divided into two doses on the first day
• Maintenance dose: 1 mg/lb (2.2 mg/kg) of body weight daily as a single dose or divided into two doses
• For severe infections: Up to 2 mg/lb (4.4 mg/kg) of body weight may be used
• For children >100 lbs: Use adult dosing 1
• Note: Not recommended for children under 8 years of age due to risk of dental discoloration 2

Infection-Specific Dosing

Skin and Soft Tissue Infections (SSTI)

• MSSA/MRSA infections: 100 mg twice daily orally 2
• Duration: 5-10 days for outpatient SSTI 2

Sexually Transmitted Infections

• Uncomplicated chlamydial infections: 100 mg twice daily for 7 days 1
• Nongonococcal urethritis: 100 mg twice daily for 7 days 1
• Uncomplicated gonococcal infections: 100 mg twice daily for 7 days 1
• Alternative single-visit dose for gonorrhea: 300 mg followed by another 300 mg one hour later 1

Other Specific Infections

• Syphilis (early): 100 mg twice daily for 2 weeks (for penicillin-allergic patients) 1
• Syphilis (>1 year duration): 100 mg twice daily for 4 weeks 1
• Acute epididymo-orchitis: 100 mg twice daily for at least 10 days 1
• Tularemia (mild cases): 100 mg twice daily 2
• Bubonic plague: 100 mg twice daily 2
• Malaria prophylaxis: 100 mg daily 1
• Inhalational anthrax (post-exposure): 100 mg twice daily for 60 days 1

Administration Guidelines

• Administer with adequate amounts of fluid to reduce the risk of esophageal irritation and ulceration 1
• Can be given with food or milk if gastric irritation occurs 1
• The absorption of doxycycline is not markedly influenced by simultaneous ingestion of food or milk 1

Special Considerations

Renal Impairment

• No dosage adjustment is necessary in patients with renal impairment 1

Severe Infections

• For management of more severe infections (particularly chronic urinary tract infections), 100 mg every 12 hours is recommended 1
• For complicated skin and soft tissue infections requiring hospitalization, consider parenteral therapy initially 2

Potential Side Effects and Precautions

• Common side effects include nausea, vomiting, diarrhea, and photosensitivity 3
• Avoid in pregnant women and children under 8 years of age 3
• Drug interactions may occur with antacids, dairy products, and supplements; advise patients to avoid taking doxycycline within 2 hours of these substances 3

Clinical Efficacy Considerations

• Doxycycline has shown 96.9% efficacy in treating certain bacterial infections compared to 76.4% with azithromycin in recent studies 4
• For respiratory tract infections, doxycycline has demonstrated good or very good results in 87% of patients 5
• Doxycycline has promising results for multidrug-resistant gram-negative bacterial infections, with clinical improvement in 81.3% of patients 6

Remember that therapeutic antibacterial serum activity usually persists for 24 hours following the recommended dosage, making once or twice daily dosing effective for most infections 1.