A 28-year-old woman who is four weeks postpartum presents with worsening symptoms of major depressive disorder including persistent sadness, crying spells, difficulty sleeping even when the baby sleeps, feelings of worthlessness and inadequacy as a mother, poor appetite, and difficulty bonding with her infant. She scores 18 on the Edinburgh Postnatal Depression Scale. She has a history of one prior depressive episode at age 22 that responded well to fluoxetine. She is exclusively breastfeeding and plans to continue for at least six months. She is adamant about not taking any medication that could harm her baby through breast milk. She denies suicidal or infanticidal ideation. The PMHNP needs to select an appropriate pharmacological treatment.