When is doxycycline (antibiotic) used?

Indications for Doxycycline Use in Clinical Practice

Doxycycline is indicated for the treatment of numerous bacterial infections, sexually transmitted infections, rickettsial diseases, and as prophylaxis for certain conditions, with specific dosing regimens tailored to each indication. 1

Primary Bacterial Infections

Respiratory Tract Infections

• Respiratory tract infections caused by:
  • Mycoplasma pneumoniae
  • Haemophilus influenzae
  • Streptococcus pneumoniae (upper respiratory infections)
  • Klebsiella species
• Dosage: 100 mg twice daily for 7-14 days 1

Sexually Transmitted Infections

• Chlamydial infections: 100 mg twice daily for 7 days 2
• Lymphogranuloma venereum: 100 mg twice daily for 21 days 2
• Nongonococcal urethritis caused by Ureaplasma urealyticum 1
• Uncomplicated urethral, endocervical, or rectal infections in adults caused by Chlamydia trachomatis 1
• Syphilis (when penicillin is contraindicated): Alternative treatment for infections caused by Treponema pallidum 1
• Gonorrhea (when penicillin is contraindicated): Alternative for uncomplicated gonorrhea 1
• Doxycycline PEP: 200 mg within 72 hours after condomless sex to prevent bacterial STIs (specifically for MSM and transgender women who have had a bacterial STI in the past 12 months) 3

Rickettsial and Related Diseases

• Rocky Mountain spotted fever
• Typhus fever and the typhus group
• Q fever
• Rickettsialpox
• Tick fevers caused by Rickettsiae
• Relapsing fever due to Borrelia recurrentis
• Dosage: 100 mg twice daily for 7-14 days depending on severity 1

Other Bacterial Infections

• Plague due to Yersinia pestis 3, 1
• Tularemia due to Francisella tularensis 1
• Cholera caused by Vibrio cholerae 1
• Brucellosis due to Brucella species (in conjunction with streptomycin) 1
• Bartonellosis due to Bartonella bacilliformis 1
• Granuloma inguinale caused by Calymmatobacterium granulomatis 1
• Anthrax due to Bacillus anthracis, including post-exposure prophylaxis for inhalational anthrax 3, 1

Prophylactic Uses

Malaria Prophylaxis

• Indicated for prophylaxis of malaria due to Plasmodium falciparum in short-term travelers (<4 months) to areas with resistant strains 1
• Dosage: 100 mg daily beginning 1-2 days before travel and continuing for 4 weeks after return

Lyme Disease Prophylaxis

• Single dose doxycycline (200 mg) can be used for prophylaxis after a high-risk tick bite 3

STI Post-Exposure Prophylaxis (Doxy PEP)

• For MSM and transgender women who have had a bacterial STI in the past 12 months
• Dosage: 200 mg taken within 72 hours after sex
• Should not exceed 200 mg every 24 hours 3

Non-Antimicrobial Uses

Inflammatory Conditions

• Acne: Subantimicrobial doses (40 mg modified-release) daily for moderate to severe inflammatory acne 4
  • Lower doses have fewer gastrointestinal side effects while maintaining efficacy 4
  • Anti-inflammatory properties are effective at doses lower than antimicrobial doses 5, 6

Formulation Considerations

Available Forms

• Doxycycline hyclate and doxycycline monohydrate are therapeutically equivalent but differ in GI side effect profiles 2
• Monohydrate formulation generally causes fewer GI side effects while maintaining the same clinical efficacy 2
• Delayed-release formulations can be administered once daily, potentially improving adherence 2

Important Precautions

Contraindications

• Pregnancy (risk category D)
• Children under 8 years (risk of dental staining and bone growth inhibition) 2
  • Exception: For life-threatening infections such as plague, use in children <8 years may be justified based on risk-benefit ratio 3

Side Effects

• Photosensitivity reactions (patients should use sun protection) 2
• Gastrointestinal symptoms including nausea, vomiting, esophageal erosion and ulceration 3

Clinical Decision Making

When deciding to use doxycycline, consider:

1. Confirmed or suspected pathogen susceptibility
2. Patient's age (contraindicated in children <8 years except for serious infections)
3. Pregnancy status (contraindicated)
4. Formulation choice based on GI tolerance
5. Dosing based on indication (antimicrobial vs. anti-inflammatory)

For bacterial STI prevention, doxycycline PEP should be implemented within a comprehensive sexual health approach, including risk reduction counseling, STI screening, and appropriate follow-up 3.