Final answer:
The first-line agent in the treatment of bipolar disorder is generally lithium, a mood stabilizer known for its effectiveness in controlling mood swings. Anticonvulsants and atypical antipsychotics are also considered first-line agents in certain cases of bipolar disorder.
Step-by-step explanation:
The first-line agent in the treatment of bipolar disorder is typically a mood stabilizer, such as lithium. Lithium has been a cornerstone in the management of bipolar disorder for many decades due to its ability to stabilize mood swings. Other medications, such as anticonvulsants (e.g., valproate, lamotrigine) and atypical antipsychotics (e.g., olanzapine, quetiapine), can also be used as first-line agents, particularly in more complex cases or when patients have a specific clinical presentation, such as rapid cycling or mixed episodes. These medications work by affecting neurotransmitter systems in the brain to help control symptoms of both manic and depressive episodes in bipolar disorder. However, the choice of a specific drug should be tailored to the individual's needs and may depend on factors such as side effects, the patient's psychiatric history, and potential interactions with other medications.