What is the recommended treatment with doxycycline (antibiotic) for a positive Lyme disease tick bite?

Doxycycline Prophylaxis for Lyme Disease After Tick Bite

A single 200 mg dose of doxycycline is recommended for prophylaxis after a tick bite, but ONLY when all five strict criteria are met: the tick is an identified Ixodes scapularis (blacklegged tick), it was attached for ≥36 hours, removal occurred within the past 72 hours, the bite occurred in a highly endemic area (≥20% tick infection rate), and the patient has no contraindications to doxycycline. 1

Critical Decision Algorithm

Step 1: Verify ALL Five Criteria Are Met

You must confirm every single criterion before prescribing prophylaxis 1:

• Tick species: Must be Ixodes scapularis (deer tick/blacklegged tick) in the Northeast/Upper Midwest, or occasionally Ixodes pacificus in the West (though prophylaxis is generally not recommended for I. pacificus due to infection rates <20%) 1
• Attachment duration: ≥36 hours of attachment (assess by degree of engorgement—partially or fully engorged nymphs or adults) 1
• Timing: Tick removed within the past 72 hours 1
• Geographic endemicity: Bite occurred in an area where ≥20% of ticks carry Borrelia burgdorferi 1
• No contraindications: Patient is not pregnant, breastfeeding, or <8 years old 1

If even ONE criterion is not met, do NOT give prophylaxis—use watchful waiting instead. 1

Step 2: Dosing When Criteria Are Met

Adults: Single dose of 200 mg doxycycline orally 1

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

This is a ONE-TIME dose—no additional doses are needed. 2

What NOT to Do: Common Pitfalls

• Do NOT substitute amoxicillin for prophylaxis in patients who cannot take doxycycline (pregnant women, children <8 years)—there is no evidence for effective short-course prophylaxis with alternative agents 1, 3
• Do NOT give prophylaxis for children <8 years old—use watchful waiting and treat only if Lyme disease develops 3
• Do NOT test the tick for infection—results do not reliably predict infection risk 3
• Do NOT perform serologic testing in asymptomatic patients after tick bite—antibodies take weeks to develop and testing at this stage is not useful 2, 3
• Do NOT assume prior Lyme disease provides immunity—patients can be reinfected, and the same prophylaxis criteria apply regardless of prior infection history 1

Special Populations

Children Under 8 Years Old

Prophylaxis is contraindicated due to tooth staining and bone development risks with doxycycline. 3 Management consists of:

• Prompt tick removal with fine-tipped tweezers 3
• Close observation for 30 days for erythema migrans or systemic symptoms 3
• Treatment with amoxicillin (50 mg/kg/day in 3 divided doses, maximum 500 mg per dose) for 14-21 days if Lyme disease develops 4

The actual infection risk after a tick bite is only 1-3.6%, making watchful waiting the appropriate strategy 3. Recent evidence suggests doxycycline may be safe and effective for treating (not preventing) Lyme disease in young children when needed, but this does not change prophylaxis recommendations 5.

Pregnant and Breastfeeding Women

Doxycycline is relatively contraindicated 4. Use watchful waiting and treat with amoxicillin if Lyme disease develops 4.

Post-Prophylaxis Management

Even after receiving prophylaxis, patients must:

• Monitor the bite site and entire body for 30 days for an expanding red rash (erythema migrans), which may appear as a "bull's-eye" pattern 2
• Watch for flu-like symptoms including fever, chills, fatigue, body aches, headache, and swollen lymph nodes 2
• Seek immediate medical attention if an expanding rash or systemic symptoms develop—the single prophylactic dose does not guarantee prevention 1, 2

Treatment vs. Prophylaxis: Key Distinction

If the patient already has symptoms (erythema migrans, fever, or other manifestations), this is treatment, not prophylaxis:

Adults with erythema migrans: Doxycycline 100 mg twice daily for 14 days (range 10-21 days) 4

Children ≥8 years with erythema migrans: Doxycycline 4 mg/kg/day in 2 divided doses (maximum 100 mg per dose) for 14 days 4

Children <8 years with erythema migrans: Amoxicillin 50 mg/kg/day in 3 divided doses (maximum 500 mg per dose) for 14-21 days 4

Doxycycline has the added advantage of treating co-infections like human granulocytic anaplasmosis (HGA), which can be transmitted simultaneously 4.

Evidence Quality

The prophylaxis recommendation is based on high-quality evidence from a landmark North American randomized controlled trial showing 87% efficacy 6 and a recent European trial demonstrating 67% relative risk reduction 7. However, the efficacy window is narrow—animal models show prophylaxis becomes ineffective when delayed ≥48 hours after tick removal, emphasizing the critical importance of the 72-hour criterion 6. The IDSA guidelines provide Grade A-I evidence for treatment regimens and Grade A-II evidence for prophylaxis criteria 4.