Doxycycline Dosage and Administration Guidelines
The standard adult dosage for doxycycline is 100 mg twice daily (every 12 hours), with specific duration depending on the infection being treated. 1
General Dosing Information
Adults:
- Initial dose: 200 mg on first day (100 mg every 12 hours)
- Maintenance dose: 100 mg daily, either as a single dose or 100 mg every 12 hours for more severe infections 1
Children (over 8 years of age):
- Weight ≤100 lbs: 2 mg/lb divided into two doses on first day, then 1 mg/lb daily as single dose or divided doses
- Weight >100 lbs: Use adult dosage 1
Duration of Treatment by Infection Type
| Infection | Dosage | Duration |
|---|---|---|
| Typical bacterial infections | 100 mg twice daily | 7-10 days [2] |
| Chlamydia | 100 mg twice daily | 7 days [2] |
| Nongonococcal urethritis | 100 mg twice daily | 7 days [2] |
| Uncomplicated gonorrhea | 100 mg twice daily | 7 days [1] |
| Lyme disease | 100 mg twice daily | 10-21 days [2] |
| Human Granulocytic Anaplasmosis | 100 mg twice daily | 10 days [2] |
| Syphilis (early) | 100 mg twice daily | 14 days [1] |
| Syphilis (>1 year duration) | 100 mg twice daily | 4 weeks [1] |
| Epididymo-orchitis | 100 mg twice daily | ≥10 days [1] |
| Malaria prophylaxis | 100 mg daily | Begin 1-2 days before travel, continue during travel and 4 weeks after [1] |
| Inhalational anthrax (post-exposure) | 100 mg twice daily | 60 days [1] |
| STI prevention (doxy PEP) | 200 mg single dose | Within 72 hours of exposure [3] |
Administration Guidelines
Take with food or milk if gastric irritation occurs 2
- The absorption of doxycycline is not markedly influenced by simultaneous ingestion of food or milk 1
Take with adequate fluid (full glass of water) to reduce risk of esophageal irritation and ulceration 2, 1
Remain upright for at least 30 minutes after taking doxycycline to prevent esophageal irritation 2
Avoid taking within 2 hours of antacids, iron, calcium, magnesium supplements, or dairy products, as these can reduce absorption 2
Special Considerations
Pregnancy:
- Generally contraindicated in pregnancy
- For life-threatening infections where alternatives aren't available, may be used for short periods (7-14 days) before 6 months of gestation 3
Renal Impairment:
Common Side Effects to Monitor:
- Photosensitivity (advise patients to avoid excessive sun exposure and use sunscreen) 2
- Gastrointestinal symptoms (nausea, vomiting, diarrhea) 3
- Esophageal irritation and ulceration 1
Clinical Pearls
- Doxycycline has excellent tissue penetration and bioavailability 4, 5
- Its long half-life allows for convenient twice-daily dosing 4
- It is well absorbed orally even in the presence of food 4
- For STI prevention (doxy PEP), 200 mg should be taken as a single dose within 72 hours of sexual exposure 3
Cautions
- Avoid in children under 8 years due to risk of dental staining and enamel hypoplasia 2
- Monitor for potential development of antimicrobial resistance with prolonged use 3
- Patients should be advised about potential side effects and how to mitigate them 3
Remember that doxycycline is a versatile antibiotic with excellent bioavailability and tissue penetration, making it effective for a wide range of infections when taken properly according to the recommended dosage and duration.