the reason
for speed in getting started on the meds is because the
Lyme bacteria (assuming you have Lyme) will, at a fairly early point after biting you, begin to find their way into areas of the body, such as cartilage, where the antibiotics can't easily reach. At that point, whenever it occurs, the simplest treatment, with doxycycline, then isn't able to penetrate the areas where the bacteria are hiding, and longer treatment with different meds is then needed.