1. A 57-year-old man presents with a steady, severe pain in the right hypochondrium, nausea, vomiting, and a temperature of 102 F. He states that his signs and symptoms began shortly after eating his favorite pizza with extra cheese, pepperoni, and sausage. Laboratory examination reveals a white blood cell count of 13,400/mL and a serum bilirubin value of 2.8 mg/dL. If hepatobiliary imaging reveals an obstructed cystic duct, which of the following agents would be the drug of choice for the treatment of this patient's pain?