Endocrine Pharmacology USMLE Step 1 Practice Question

A 25-year-old woman at 7 weeks gestation by last menstrual period presents to an outpatient clinic requesting medical termination of pregnancy. She has a confirmed intrauterine pregnancy on transvaginal ultrasound with a visible fetal pole and cardiac activity. Her medical history is unremarkable, and she denies smoking, use of corticosteroids, or a history of adrenal insufficiency. Vital signs are stable: BP 118/76 mmHg, HR 82 bpm, RR 16 breaths/min, and temperature 37°C. Physical examination reveals a soft, non-tender abdomen with a uterus consistent with early pregnancy. Serum β-hCG is 125,000 mIU/mL, hemoglobin is 13.4 g/dL, and Rh blood type is confirmed. She denies any vaginal bleeding prior to treatment. She is counseled on the two-drug regimen and given the first agent orally in clinic, with instructions to administer the second agent at home 24 to 48 hours later. Which drug was most likely administered first?