A 20-year-old student came to the emergency department with primary complaints of palpitations, low-grade fever, and anxiety for 2 months. She reports that she is irritable and suffers severe mood swings that is interfering with her sleep and relationships (she admits to crying spells and frequent fights with friends and family). She has also lost 12 pounds in the past 2 months with no apparent alteration in her diet or physical activity (though she is happy with her weight loss). She denies any past medical problems, though her friends have always been worried that she eats too little.
Her temperature is 38.0 C (100.4 F), blood pressure is 148/62 mm Hg, pulse is 122/min and regular, and respiratory rate is 28/min. Examination reveals a bruit heard over the anterior neck, fine tremor of the hands, and warm, moist skin. Her eyes and eyelids do not move together during finger following test (with steady head). Laboratory work is sent, including a thyroid panel, but will not be available until tomorrow morning.
Which of the following is the most appropriate initial management at this time?