What is the recommended prophylactic antibiotic treatment for Lyme disease after a tick bite?

Tick Bite Management and Lyme Disease Prophylaxis

A single dose of doxycycline (200 mg for adults, 4.4 mg/kg up to 200 mg for children ≥8 years) is recommended for Lyme disease prophylaxis only when all high-risk criteria are met: identified Ixodes tick attached for ≥36 hours, bite occurred in a highly endemic area (≥20% tick infection rate), treatment can be started within 72 hours of tick removal, and doxycycline is not contraindicated. 1, 2

High-Risk Criteria for Prophylactic Treatment

• Prophylactic antibiotic treatment should only be given when ALL of the following criteria are met:
  • The tick is identified as an Ixodes species (I. scapularis or I. pacificus) 1, 2
  • The tick was attached for ≥36 hours (based on engorgement or known time of exposure) 1
  • The bite occurred in a highly endemic area with ≥20% tick infection rates (parts of New England, mid-Atlantic states, Minnesota, Wisconsin) 1
  • Treatment can be started within 72 hours of tick removal 1, 2
  • Doxycycline is not contraindicated for the patient 1, 2

Recommended Prophylactic Regimen

• For adults and children ≥8 years: Single dose of oral doxycycline 200 mg 1, 2
• For children ≥8 years: Single dose of oral doxycycline 4.4 mg/kg (maximum 200 mg) 1, 2
• Doxycycline is relatively contraindicated in pregnant women and children <8 years 1
• Amoxicillin is NOT recommended as a substitute for prophylaxis in those who cannot take doxycycline due to:
  • Lack of data on effective short-course regimens 1
  • Need for multi-day regimens with associated adverse effects 1
  • Excellent efficacy of antibiotic treatment if Lyme disease develops 1
  • Extremely low risk of serious complications from Lyme disease after recognized tick bite 1

Evidence Supporting Prophylaxis

• A single dose of doxycycline has been shown to be 67-87% effective in preventing Lyme disease after high-risk tick bites 3, 4
• The number needed to treat to prevent one case of Lyme disease is approximately 51 4
• Prophylaxis is most effective when administered promptly after tick removal, with significantly reduced efficacy when delayed beyond 24 hours 5

When Prophylaxis is NOT Recommended

• For low-risk or equivocal risk tick bites 1
• For bites from Ixodes pacificus ticks (Western blacklegged tick) in most regions due to low infection rates 1
• When the tick cannot be reliably identified as an Ixodes species 1, 2
• When the tick has been attached for less than 36 hours 1
• When more than 72 hours have elapsed since tick removal 1
• In areas with low rates (<20%) of B. burgdorferi infection in ticks 1

Post-Exposure Monitoring

• All persons with tick bites, including those who received prophylaxis, should be monitored for 30 days for:
  • Expanding skin lesion at the bite site (erythema migrans) 1, 6
  • Flu-like symptoms 6
  • Other signs of tick-borne diseases 1, 2
• If symptoms develop, patients should seek medical attention for appropriate diagnostic testing and treatment 1

Important Considerations

• Prophylactic antibiotics do not prevent other tick-borne diseases such as anaplasmosis or babesiosis 1, 6
• A wait-and-watch approach is recommended if a tick bite cannot be classified with high certainty as high-risk 1, 2
• Recent evidence suggests doxycycline may be better tolerated in children <8 years than previously thought, but amoxicillin remains the preferred treatment if Lyme disease develops in this age group 7
• The efficacy of prophylaxis decreases significantly when administered more than 24 hours after tick removal, highlighting the importance of prompt treatment 5

Prevention of Future Tick Bites

• Use protective clothing and EPA-registered tick repellents 2, 6
• Perform daily full-body tick checks 2, 6
• Remove attached ticks promptly using fine-tipped tweezers 2, 6
• Wash bite areas with soap and water after tick removal 6