The client suffers from bipolar disorder. The client is experiencing a downward spiral. For which drug should the nurse expect the client to require serum level monitoring?

In the treatment of bipolar disorder, specifically during a downward spiral (depressive episode) or a manic phase, mood stabilizers are the gold standard. Lithium carbonate is unique because it is an element (a salt) with a remarkably narrow therapeutic index, meaning the difference between a therapeutic dose and a toxic dose is very small. Rationale: A. Bupropion is an atypical antidepressant. Although it is sometimes used in bipolar depression, it does not require routine serum level monitoring. Furthermore, antidepressants must be used with extreme caution in bipolar patients as they can overshoot the target and trigger a switch into mania. B. Lithium is the correct answer. Because lithium is excreted almost entirely by the kidneys and is handled by the body similarly to sodium, factors like dehydration or changes in salt intake can cause levels to rise dangerously. Regular blood draws are mandatory to ensure the serum level remains within the therapeutic range of 0.6 to 1.2 mEq/L. Levels above 1.5 mEq/L can lead to severe toxicity, including tremors, confusion, seizures, and death. C. Although some anticonvulsants used as mood stabilizers (like valproic acid or carbamazepine) do require serum monitoring, anticonvulsants is a broad category. In nursing board exams, if Lithium is an option alongside a general category, Lithium is the most correct answer because its monitoring is more frequent, critical, and specific to the drug's safety profile. D. Fluoxetine is an SSRI. Like Bupropion, it does not require blood level monitoring. Its use in Bipolar Disorder is typically limited to being paired with an antipsychotic (like Olanzapine) to prevent the induction of mania.