Question

During a late June clinic visit in Massachusetts, a $28$-year-old pregnant woman at $18$ weeks gestation presents for evaluation of an expanding rash. She reports feeling unusually fatigued over the past $4$ days, accompanied by a mild headache. Two weeks ago, the patient spent a weekend camping in a heavily wooded area, though she does not recall any specific insect bites. Her medical history is notable for a childhood episode of anaphylaxis following penicillin administration, which required emergent intubation. Vital signs include a temperature of $37.4^\circ\text{C}$, heart rate of $88\text{/min}$, and blood pressure of $110/70\text{ mm Hg}$. Physical examination reveals a $9\text{-cm}$ annular, erythematous plaque with central clearing on the right posterior thigh. The lesion is warm but non-tender. The remainder of the examination, including a detailed neurological assessment, is unremarkable. Which of the following is the most appropriate pharmacotherapy for this patient?