Prophylactic Antibiotic Recommendations for Tick Bites
A single dose of oral doxycycline (200 mg for adults, 4.4 mg/kg up to 200 mg for children ≥8 years) is the recommended prophylactic antibiotic for tick bites, but only when administered within 72 hours of removing a high-risk tick. 1
Criteria for Prophylactic Treatment
Prophylactic antibiotic therapy should be given only when ALL of the following criteria are met:
- The tick is identified as an Ixodes species (deer tick/blacklegged tick) 1, 2
- The tick was attached for ≥36 hours (based on engorgement or known time of attachment) 1
- The bite occurred in a highly endemic area (≥20% tick infection rates, such as parts of New England, mid-Atlantic states, Minnesota, Wisconsin) 1, 2
- Doxycycline can be administered within 72 hours of tick removal 1, 2
- Doxycycline is not contraindicated for the patient 1, 2
Recommended Dosing
- Adults: Single oral dose of 200 mg doxycycline 1
- Children ≥8 years: Single oral dose of 4.4 mg/kg (maximum 200 mg) 1, 2
When Prophylaxis is NOT Recommended
- For tick bites that don't meet ALL high-risk criteria listed above 1
- For bites from Ixodes pacificus (western blacklegged tick) 1
- When more than 72 hours have elapsed since tick removal 1, 3
- For pregnant women and children <8 years (doxycycline is relatively contraindicated) 1, 2
- For asymptomatic patients following tick bites (testing is not recommended) 1, 4
Alternative Approach When Prophylaxis is Not Indicated
- A "wait-and-watch" approach is recommended when a tick bite cannot be classified with high certainty as high-risk 1
- The Infectious Diseases Society of America does not recommend substituting amoxicillin for doxycycline in persons for whom doxycycline is contraindicated 1
- Monitor for symptoms of Lyme disease for 30 days, particularly watching for erythema migrans (expanding "bull's-eye" rash) at the bite site 4, 3
- Watch for flu-like symptoms including fever, chills, fatigue, body aches, headache, and swollen lymph nodes 4, 3
Effectiveness of Prophylaxis
- When administered according to guidelines, single-dose doxycycline prophylaxis has shown a 67-87% relative risk reduction in preventing Lyme disease 5, 6
- The number needed to treat is approximately 51, meaning about 51 people need to receive prophylaxis to prevent one case of Lyme disease 5
- Prophylactic effectiveness decreases significantly when treatment is delayed beyond 24 hours after tick removal 6
Prevention of Future Tick Bites
- Use EPA-registered repellents (DEET, picaridin, IR3535, oil of lemon eucalyptus, PMD, 2-undecanone) on exposed skin 1, 2
- Apply permethrin to clothing for additional protection 1, 2
- Wear protective clothing including long-sleeved shirts, pants, and closed-toe shoes 2
- Perform daily full-body tick checks when in tick-endemic areas 4, 2
- Remove attached ticks promptly using fine-tipped tweezers, grasping the tick as close to the skin surface as possible 1, 7
Common Pitfalls to Avoid
- Delaying prophylaxis beyond 72 hours after tick removal (effectiveness decreases significantly) 6
- Administering prophylaxis for all tick bites regardless of risk factors 1
- Burning ticks or applying petroleum products to remove them (use mechanical removal with tweezers) 1
- Testing asymptomatic patients for Lyme disease after tick bites 1
- Underprescribing prophylaxis for eligible children (who are disproportionately affected by Lyme disease) 8