A 48-year-old man is evaluated in the outpatient clinic for a 6-week history of persistent… — USMLE Step 2 CK

A 48-year-old man is evaluated in the outpatient clinic for a 6-week history of persistently low mood, severe fatigue, anhedonia, and waking up at 3:00 AM every day without being able to return to sleep. He reports feeling "completely empty" and has unintentionally lost $4.5\text{ kg}$ ( $10\text{ lb}$ ) over this period. His past medical history is significant for chronic lumbar radiculopathy, for which he takes daily tramadol. His past psychiatric history reveals a psychiatric hospitalization at age 32 for a 3-week episode of abnormally euphoric mood, hypersexuality, decreased need for sleep, and impulsive spending that led to significant debt. Vital signs are within normal limits. Physical examination is unremarkable. Mental status examination reveals a disheveled man with psychomotor retardation, restricted affect, and depressed mood. He denies active suicidal ideation. Laboratory studies show a thyroid-stimulating hormone (TSH) level of $1.8\text{ }\mu\text{U/mL}$ and a free thyroxine (T4) level of $1.2\text{ ng/dL}$ . Which of the following is the most appropriate next step in management?

Initiate lurasidoneAnswer
B
Initiate sertraline
C
Initiate venlafaxine
D
Initiate levothyroxine
E
Initiate selegiline

Answer

The most appropriate next step is to initiate lurasidone, a second-generation antipsychotic approved for bipolar depression.

The patient's current presentation of low mood, anhedonia, weight loss, and early morning awakenings meets the criteria for a major depressive episode. However, his history of a prior hospitalization for euphoric mood, decreased need for sleep, and impulsivity is highly characteristic of a manic episode. Therefore, his correct diagnosis is bipolar I disorder, currently in a depressed episode. The standard of care for acute bipolar depression includes specific second-generation antipsychotics (e.g., lurasidone, quetiapine, cariprazine) or mood stabilizers (e.g., lithium, lamotrigine). Initiating lurasidone is the most appropriate next step to effectively treat his depressive symptoms without the risk of inducing mania.

Step-by-Step Solution

Identify the patient's current clinical syndrome.

The patient is presenting with a major depressive episode (low mood, fatigue, anhedonia, early morning awakening, weight loss).

Establishing the current phase of the illness is necessary to guide symptom-specific therapy.

Review the patient's past psychiatric history.

The patient has a history of a distinct manic episode at age 32 (euphoria, hypersexuality, decreased sleep, impulsive spending requiring hospitalization).

A history of mania changes the diagnosis from major depressive disorder to bipolar I disorder.

Select the appropriate pharmacotherapy for bipolar depression while avoiding contraindications.

Lurasidone is selected over antidepressant monotherapies (which risk manic switch) and over medications that interact with his current regimen.

Lurasidone is approved for acute bipolar depression. Antidepressants like sertraline or venlafaxine are avoided as monotherapy in bipolar I disorder. Selegiline is avoided due to interactions with tramadol.

Key Concept

Patients presenting with depressive episodes must be screened for a history of mania; if present, the diagnosis is bipolar I disorder, and treatment involves mood stabilizers or specific atypical antipsychotics (e.g., lurasidone, quetiapine) rather than antidepressant monotherapy.

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