a 25-year-old female comes with reports of a sudden onset of increased thirst and urination. this began abruptly 1 week ago and has not abated since. she states that since that time she has been thirsty all the time. the only significant illness in her life has been the recent diagnosis of bipolar affective illness subtype i that was made 6 weeks ago. she was started on lithium carbonate and is currently taking 1200 mg/day. her serum lithium levels have been normal since the beginning. on examination, her bp is 110/70 mm hg. she has lost 5 pounds during the last week and looks somewhat dehydrated. what is the treatment of choice in this patient?