A 31-year-old woman is evaluated in the emergency department on postpartum day 4 after her husband called 911 because she was talking to people who were not present, had not slept in 3 days, was speaking rapidly, and expressed the belief that her newborn had special powers. She has no prior psychiatric history but her mother has bipolar I disorder. She is breastfeeding and expresses a strong desire to continue. Physical examination and laboratory workup including thyroid function, complete metabolic panel, CBC, urinalysis, and urine toxicology are unremarkable. She is medically cleared and transferred to the inpatient psychiatric unit. Which pharmacotherapy plan is most appropriate?