American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the key advantage of using doxycycline in treating Lyme disease compared to amoxicillin?

1. It is more effective for Lyme disease

2. It also treats Anaplasma phagocytophila

3. It has a lower rate of side effects

4. It is cheaper than amoxicillin

The correct answer is: It also treats Anaplasma phagocytophila

Doxycycline is particularly advantageous in treating Lyme disease because it also effectively targets co-infections such as Anaplasma phagocytophila, a tick-borne pathogen that can be transmitted at the same time as Lyme disease. This dual action is important in areas where co-infections are prevalent, as it simplifies treatment regimens and can improve patient outcomes by addressing multiple infections simultaneously. While amoxicillin is effective for Lyme disease, it does not provide coverage for Anaplasma phagocytophila. This limitation means that when physicians suspect or confirm co-infection, they may need to prescribe an additional antibiotic if amoxicillin were chosen as the treatment for Lyme disease. Therefore, doxycycline’s ability to treat both Lyme disease and Anaplasma phagocytophila makes it a valuable choice in managing patients who may have mixed infections. In terms of side effects, costs, and effectiveness specifically for Lyme disease, these factors could vary based on individual patient circumstances and regional differences in bacterial resistance, but the clear advantage lies in the broad-spectrum efficacy of doxycycline against multiple pathogens.