In September, Stefanie Davis, 31, got the right medicine, Adderall, but the wrong dose. She pulled over on the interstate after feeling short of breath and dizzy with blurred vision. The pills, dispensed by a Walgreens in Sun City Center, Florida, were each 30 milligrams instead of her usual 20. She is fighting with Walgreens to cover a $900 bill for her visit to an emergency room.