A37-year-old woman is brought to the emergency department 30 minutes after the onset of a severe occipital headache, palpitations, and tremulousness. shortly before this episode, she ate several slices of pepperoni pizza. she has a 2-month history of atypical major depressive disorder treated with phenelzine. she is otherwise healthy. she appears anxious and tremulous. her temperature is 37.8°c (100°f), pulse is 94/min, respirations are 20/min, and blood pressure is 210/110 mm hg. physical examination shows no other abnormalities. the most appropriate next step is administration of