A 34-year-old man with bipolar disorder type I presents to the emergency department after a suicide attempt by pesticide ingestion 2 hours ago. He reports feeling hopeless and states 'I don't deserve to live.' On examination, he is alert, oriented, and cooperative. His wife reports he has been non-compliant with lithium for 3 months due to side effects. Vital signs are stable. What is the most appropriate immediate next step in management?