Q. A 35-year-old woman presents to her primary care physician with a six-month history of excessive thirst, frequent urination, and weight loss. She also reports a history of fatigue and difficulty regulating her blood sugar levels. The patient's vital signs on presentation are as follows: afebrile, blood pressure 120/80 mm Hg, pulse rate 80/minute, and respiratory rate 18/minute. Physical examination reveals a patient with weight loss and signs of dehydration. Further evaluation reveals elevated levels of glucose in the patient's blood and a positive autoimmune screen for type 1 diabetes mellitus. The patient is also found to have central diabetes insipidus. The patient is started on insulin therapy to regulate her blood glucose levels and is treated with vasopressin to reduce her excessive thirst and frequent urination. She is also taking oral contraceptive pills (OCPs) for birth control and cimetidine for peptic ulcer disease. Which of these medications acts via attachment to intracellular receptors?