Bicillin shots usually follow a high dose penicillin oral. the point is to trick the Lyme into dropping it's guard when it thinks the high dose oral is dissipating from the body and hoping it won't notice the low dose shots still in your system thusly killing the little buggers. My shots didn't hurt too much b/c the nurse did them higher up in my glut. If you get someone who shoots it in the center of the cheek --ouchee. Good thing it's only 1x a week.