What alternative antibiotic to doxycycline (doxy) can be used for Lyme disease prophylaxis in a high-risk patient in their 3rd trimester of pregnancy with a tick bite less than 48 hours prior?

Alternative Antibiotics for Lyme Disease Prophylaxis in Third Trimester Pregnancy

For a high-risk patient in the third trimester of pregnancy with a tick bite less than 48 hours prior, amoxicillin is the recommended alternative to doxycycline for Lyme disease prophylaxis when prophylaxis is deemed necessary. 1, 2, 3

Risk Assessment for Tick Bite

• High-risk tick bite criteria include: Ixodes species vector (blacklegged tick), occurrence in highly endemic areas (parts of New England, mid-Atlantic states, Minnesota, Wisconsin), and tick attachment for ≥36 hours 2
• Tick attachment of less than 24-48 hours carries a low risk of disease transmission, as it typically takes more than 24 hours of attachment to transfer Borrelia burgdorferi 3, 4
• Prompt removal of the tick is the most important first step in prevention 3

Management Algorithm for Tick Bites in Pregnancy

First-line approach:

• The preferred approach is "wait and watch" for signs and symptoms of infection for 30 days, monitoring specifically for erythema migrans (bull's-eye rash) at the bite site 2, 3
• Prophylactic antibiotics are generally not recommended after tick bites in persons who are not ill, regardless of pregnancy status 3

When prophylaxis is deemed necessary (high-risk patient):

• Amoxicillin 500 mg three times daily for 7-10 days can be used as an alternative to doxycycline for Lyme disease prophylaxis in pregnant women 1, 3
• The IDSA guidelines indicate that for adult patients intolerant of doxycycline, amoxicillin is a first-line alternative 1

Important Considerations

• Doxycycline is relatively contraindicated during pregnancy, making amoxicillin the preferred alternative 1, 4
• If Lyme disease develops during pregnancy, amoxicillin 500 mg three times daily for 14 days is the preferred treatment 2, 5
• For severe cases where Lyme disease is confirmed with neurological involvement, intravenous ceftriaxone 2 g daily for 14 days may be considered 6
• Clinical and epidemiological studies suggest favorable outcomes when pregnant women with Lyme disease receive standard antibiotic treatment 2, 4

Alternative Options

• For patients allergic to penicillins, cefuroxime axetil (500 mg twice per day) can be used as an alternative 1
• Macrolide antibiotics (azithromycin, clarithromycin, or erythromycin) should only be used when patients cannot tolerate amoxicillin, doxycycline, and cefuroxime axetil 1
• Patients treated with macrolides should be closely observed to ensure resolution of clinical manifestations 1

Common Pitfalls to Avoid

• Unnecessary prophylactic antibiotic use in pregnancy carries risks, including drug-associated rash and other adverse effects 2, 3
• First-generation cephalosporins, such as cephalexin, are ineffective for treatment of Lyme disease and should not be used 1
• Delaying treatment if signs of Lyme disease develop can lead to more serious complications 3
• The window for effective prophylactic treatment is narrow - studies suggest prophylaxis becomes ineffective when delivered ≥2 days after tick removal 7