Final answer:
Antipsychotics are usually the first choice of medication to treat postpartum psychosis, with chlorpromazine as a common example. Lithium may also be used when associated with bipolar disorder.
Step-by-step explanation:
The first drug of choice to treat postpartum psychosis is typically an antipsychotic medication. These drugs, including agents such as chlorpromazine or newer antipsychotics like risperidone and clozapine, are central to managing psychosis symptoms, such as hallucinations and delusions. In some cases, a mood stabilizer like lithium may be used, particularly if the postpartum psychosis is part of a bipolar disorder. It is important to note that the exact medication and treatment plan should be tailored to the individual patient by a healthcare provider.