When can doxycycline (tetracycline antibiotic) be given?

Doxycycline Administration Guidelines

Doxycycline can be given for bacterial infections, with specific indications for sexually transmitted infections, and as post-exposure prophylaxis for high-risk populations, with dosing typically 100 mg twice daily for treatment and 200 mg as a single dose for prophylaxis. 1, 2

General Dosing Recommendations

• For adults, the standard treatment dose is 200 mg on the first day (100 mg every 12 hours), followed by a maintenance dose of 100 mg daily or 100 mg every 12 hours for more severe infections 1
• For children over 8 years of age weighing less than 100 pounds, the recommended dosage is 2 mg/lb divided into two doses on the first day, followed by 1 mg/lb daily (single dose or divided) 1
• For children over 100 pounds, the adult dosage should be used 1
• Doxycycline should be taken with adequate fluid to prevent esophageal irritation 1
• If gastric irritation occurs, doxycycline can be taken with food or milk without significantly affecting absorption 1

Specific Indications and Dosing

Sexually Transmitted Infections

• Uncomplicated chlamydial infections: 100 mg orally twice daily for 7 days 1, 2
• Nongonococcal urethritis caused by C. trachomatis or U. urealyticum: 100 mg orally twice daily for 7 days 1
• Uncomplicated gonococcal infections: 100 mg orally twice daily for 7 days (alternative: 300 mg followed by another 300 mg one hour later) 1
• Early syphilis in penicillin-allergic patients: 100 mg orally twice daily for 2 weeks 1
• Late syphilis in penicillin-allergic patients: 100 mg orally twice daily for 4 weeks 1
• Acute epididymo-orchitis: 100 mg orally twice daily for at least 10 days 1

Post-Exposure Prophylaxis for STIs

• The CDC recommends doxycycline as post-exposure prophylaxis (doxy PEP) for gay, bisexual, and other men who have sex with men (MSM) and transgender women (TGW) with a history of at least one bacterial STI in the past 12 months 3
• The recommended prophylactic dose is 200 mg taken as soon as possible within 72 hours after sexual contact, not exceeding 200 mg per 24 hours 3
• This approach has been shown to reduce transmission of syphilis, gonorrhea, and chlamydia by approximately two-thirds in high-risk populations 4

Other Indications

• Malaria prophylaxis: 100 mg daily for adults; 2 mg/kg daily for children over 8 years (not exceeding adult dose) 1
• Inhalational anthrax (post-exposure): 100 mg twice daily for 60 days for adults; 1 mg/lb twice daily for children under 100 lbs 1
• Skin and soft tissue infections, including MRSA: 100 mg orally twice daily 2
• Urinary tract infections: Short courses (4 days) may be as effective as longer courses (10 days) for uncomplicated cystitis 5

Important Precautions and Contraindications

• Doxycycline is contraindicated in pregnancy and in children under 8 years of age 2
• Common adverse effects include photosensitivity, gastrointestinal symptoms, and esophageal erosion 2
• To minimize side effects:
  • Take with a full glass of water 3
  • Take on a full stomach 3
  • Avoid lying down for at least 1 hour after taking 3
  • Separate doses by at least 2 hours from dairy products, antacids, and supplements containing calcium, iron, magnesium, or sodium bicarbonate 3

Implementation of Doxycycline PEP

• When prescribing doxycycline as PEP, implement within a comprehensive sexual health approach 3:
  • Screen for STIs at anatomic sites of exposure 3
  • Provide risk reduction counseling 3
  • Discuss HIV PrEP or treatment as indicated 3
  • Counsel on potential side effects and drug interactions 3
  • Assess ongoing need for doxy PEP every 3-6 months 3

Special Considerations

• Doxycycline also has anti-inflammatory properties that make it useful for treating non-infectious conditions such as hair follicle diseases and certain vascular proliferations 6
• No clinically relevant interactions between doxycycline and gender-affirming hormonal therapy have been reported 3
• For certain bacterial infections like Bartonella, longer treatment courses may be necessary for effective eradication 7
• When treating Lyme disease with erythema migrans, doxycycline's principal advantage over tetracycline is convenience of less frequent dosing 8