What is the recommended prophylactic antibiotic for a tick bite?

Prophylactic Antibiotic for Tick Bite

A single dose of doxycycline (200 mg for adults, 4 mg/kg up to 200 mg for children ≥8 years) is the recommended prophylactic antibiotic for tick bites, but only when specific high-risk criteria are met. 1

Criteria for Prophylactic Treatment

Prophylactic antibiotics should only be given when ALL of the following criteria are met:

• The tick is identified as an adult or nymphal Ixodes scapularis (deer tick)
• The tick was attached for ≥36 hours
• Prophylaxis can be started within 72 hours of tick removal
• The local rate of tick infection with Borrelia burgdorferi is ≥20% (endemic area)
• The patient has no contraindications to doxycycline 1

If these criteria are not all met, a "wait and watch" approach is recommended, with monitoring for 30 days for symptoms of tick-borne illness.

Dosing and Administration

• Adults: Single dose of doxycycline 200 mg orally
• Children ≥8 years: Single dose of doxycycline 4 mg/kg (maximum 200 mg) orally 1

Special Populations

• Pregnant or breastfeeding women: Doxycycline is contraindicated
• Children <8 years: Doxycycline is contraindicated
• Alternative for these populations: Amoxicillin is not officially recommended as prophylaxis due to lack of data on effective short-course regimens, but may be considered 1

Efficacy

Prophylactic doxycycline has demonstrated significant effectiveness in preventing Lyme disease after high-risk tick bites:

• A European randomized controlled trial showed a 67% relative risk reduction with a number-needed-to-treat of 51 2
• Research suggests that timing is critical - prophylaxis is most effective when administered promptly after tick removal, with significantly reduced efficacy when delayed beyond 24 hours 3

Common Pitfalls to Avoid

1. Overuse of prophylaxis: Do not prescribe prophylaxis if the tick was attached for less than 36 hours, if more than 72 hours have passed since removal, or if the tick cannot be reliably identified as Ixodes scapularis 1

2. Neglecting prevention measures: Emphasize preventive measures such as using EPA-registered repellents, wearing protective clothing, treating clothing with permethrin, and performing regular tick checks 1

3. Confusing prophylaxis with treatment: A single dose of doxycycline is for prophylaxis only. If symptoms of Lyme disease develop (expanding red rash ≥5 cm, fever, headache, fatigue, muscle/joint pain), a complete course of antibiotics is required 1

4. Routine serologic testing: This is not recommended after a tick bite in asymptomatic individuals 1

5. Inappropriate tick removal: Advise proper tick removal using fine-tipped tweezers or forceps, grasping the tick as close to the skin as possible and pulling upward with steady pressure 1

Recent research indicates that Lyme disease prophylaxis may be underprescribed for certain groups, particularly children 4, highlighting the importance of following evidence-based guidelines for appropriate prophylaxis.