What is the treatment for a patient with a suspected Lyme disease tick bite, presenting with a bullseye rash, considering age and potential allergies to antibiotics (antibiotic hypersensitivity)?

Treatment for Bullseye Rash After Tick Bite

For a patient presenting with a bullseye rash (erythema migrans), start doxycycline 100 mg twice daily for 10 days as first-line treatment, or use amoxicillin 500 mg three times daily for 14 days if the patient is pregnant, under 8 years old, or has a doxycycline allergy. 1

Diagnosis Confirmation

• The bullseye rash (erythema migrans) is pathognomonic for Lyme disease in patients with potential tick exposure in endemic areas, meaning the clinical diagnosis alone is sufficient without laboratory testing 1
• Do not delay treatment waiting for serologic confirmation, as antibody testing is not recommended for typical erythema migrans 1

First-Line Treatment Algorithm

For Most Patients (Age ≥8 years, Not Pregnant, No Doxycycline Allergy):

• Doxycycline 100 mg orally twice daily for 10 days 1
• This is the preferred agent with the strongest evidence base 2, 1
• For children ≥8 years: doxycycline 4 mg/kg per day in 2 divided doses (maximum 100 mg per dose) 2

For Pregnant Women, Children <8 Years, or Doxycycline-Allergic Patients:

• Amoxicillin 500 mg orally three times daily for 14 days 2, 1
• Alternative dosing: 500 mg four times daily for 14 days 1
• For children: standard pediatric dosing applies 2
• Amoxicillin is the preferred alternative in these populations 1

Alternative Beta-Lactam Option:

• Cefuroxime axetil 500 mg orally twice daily for 14 days 2, 1
• Use if patient cannot tolerate both doxycycline and amoxicillin 1

Management of Multiple Antibiotic Allergies

If Patient Cannot Take Doxycycline AND Beta-Lactams:

• Azithromycin 500 mg orally daily for 7-10 days (preferably 7 days) 1
• Alternative macrolides for adults: clarithromycin 500 mg twice daily for 14-21 days (if not pregnant) or erythromycin 500 mg four times daily for 14-21 days 2
• Important caveat: Macrolides are significantly less effective than first-line agents and should only be used when no other options exist 2
• Patients on macrolides require close monitoring to ensure clinical resolution 2

Pediatric Macrolide Dosing (When Necessary):

• Azithromycin: 10 mg/kg per day (maximum 500 mg/day) 2
• Clarithromycin: 7.5 mg/kg twice daily (maximum 500 mg per dose) 2
• Erythromycin: 12.5 mg/kg four times daily (maximum 500 mg per dose) 2

Critical Pitfalls to Avoid

• Do not use amoxicillin for prophylaxis in patients who cannot take doxycycline after a tick bite without rash—there is no evidence for effective short-course prophylactic regimens, and treatment is highly effective if infection develops 2, 3
• Do not extend treatment duration beyond recommended periods without clear indication—there is no evidence that longer therapy improves outcomes for early Lyme disease 2
• Do not substitute macrolides as first-line therapy—they have proven inferior efficacy compared to doxycycline, amoxicillin, and cefuroxime 2

Post-Treatment Monitoring

• Patients should be monitored for resolution of the rash and associated symptoms 2
• If symptoms persist or worsen despite appropriate antibiotic therapy, reassess for alternative diagnoses or complications 2
• In geographic regions where Southern tick-associated rash illness (STARI) overlaps with Lyme disease, treat as Lyme disease when distinction cannot be made 1

Prevention of Future Tick Bites

• Use EPA-registered repellents (DEET, picaridin, IR3535, or oil of lemon eucalyptus) 1
• Wear protective clothing when in tick-endemic areas 1
• Perform daily full-body tick checks after outdoor activities 1
• Remove ticks promptly using fine-tipped tweezers 1