Doxycycline Monohydrate Dosage and Usage for Bacterial Infections
For bacterial infections, doxycycline monohydrate is typically administered at 100 mg twice daily for adults, with specific durations based on the infection type. 1
Adult Dosing Regimens
- The standard adult dosage is 200 mg on the first day (administered as 100 mg every 12 hours), followed by a maintenance dose of 100 mg/day for most infections 1
- For more severe infections, 100 mg every 12 hours is recommended throughout the treatment course 1
- For skin infections, 100 mg twice daily for 7-14 days is the recommended regimen 2
- For uncomplicated gonococcal infections: 100 mg twice daily for 7 days, or alternatively a single-visit dose of 300 mg followed by another 300 mg one hour later 1
- For uncomplicated urethral, endocervical, or rectal infections caused by Chlamydia trachomatis: 100 mg twice daily for 7 days 1
- For nongonococcal urethritis (NGU): 100 mg twice daily for 7 days 1
- For early syphilis in penicillin-allergic patients: 100 mg twice daily for 2 weeks 1
- For syphilis of more than one year's duration: 100 mg twice daily for 4 weeks 1
- For acute epididymo-orchitis: 100 mg twice daily for at least 10 days 1
Pediatric Dosing Regimens
- For children above 8 years of age weighing 100 pounds or less: 2 mg/lb of body weight divided into two doses on the first day, followed by 1 mg/lb of body weight daily (single dose or divided into two doses) 1
- For more severe infections: up to 2 mg/lb of body weight may be used 1
- For children over 100 pounds: use the standard adult dose 1
- Doxycycline should not be used in children under 8 years of age due to risk of permanent tooth discoloration and enamel hypoplasia 1
Special Infections
Human Granulocytic Anaplasmosis (HGA)
- For adults with HGA: 100 mg twice daily orally (or intravenously if unable to take oral medication) for 10 days 3
- For children with HGA: 4 mg/kg per day in 2 divided doses (maximum 100 mg per dose) 3
- Treatment should not be delayed in patients with suggestive clinical presentation pending laboratory confirmation 3
STI Prophylaxis
- For post-exposure prophylaxis: 200 mg as a single dose within 72 hours after potential exposure, not exceeding 200 mg per 24 hours 4
Malaria Prophylaxis
- For adults: 100 mg daily 1
- For children over 8 years: 2 mg/kg daily (up to adult dose) 1
- Prophylaxis should begin 1-2 days before travel to malarious areas and continue daily during travel and for 4 weeks after leaving 1
Inhalational Anthrax (Post-Exposure)
- Adults: 100 mg twice daily for 60 days 1
- Children weighing less than 100 lb: 1 mg/lb (2.2 mg/kg) twice daily for 60 days 1
- Children weighing 100 lb or more: use adult dose 1
Administration Guidelines
- Administer with adequate amounts of fluid to reduce the risk of esophageal irritation and ulceration 1
- If gastric irritation occurs, doxycycline can be given with food or milk 1
- The absorption of doxycycline is not markedly influenced by simultaneous ingestion of food or milk 1
- Complete the full course of therapy even if symptoms improve before completion 2
Common Pitfalls and Considerations
- Inadequate duration of therapy (less than 7 days for most infections) may lead to treatment failure 2
- No dosage adjustment is typically required for patients with renal impairment 1
- For patients with mild HGA who cannot take doxycycline (drug allergy, pregnancy, age < 8 years), rifampin can be used as an alternative (300 mg twice daily for adults, 10 mg/kg twice daily for children) 3
- Monitor closely for resolution of clinical and laboratory abnormalities in patients treated with alternative agents 3
Efficacy and Spectrum
- Doxycycline is effective against a wide range of pathogens including those causing respiratory infections, urinary tract infections, and skin infections 5
- It is particularly effective against intracellular pathogens and is the drug of choice for infections caused by Rickettsia, Borrelia, and Ehrlichia 5
- For methicillin-resistant Staphylococcus aureus (MRSA) skin infections, doxycycline is an effective oral treatment option 2