Examkin

Question

Difficulty: Very hardBipolar and Related Disorders

A 34-year-old man comes to the psychiatry clinic reporting a 6-week history of worsening depressed mood, anhedonia, and profound fatigue. He states he is sleeping up to 14 hours a day and has gained 6 kg (13.2 lb) during this period. The patient has a history of a seizure disorder that has been well controlled on carbamazepine for the past 8 years. Five years ago, he was prescribed sertraline by his primary care physician for a depressive episode; three weeks later, he developed grandiosity, decreased need for sleep, pressured speech, and reckless spending. This resulted in a psychiatric hospitalization. He required inpatient observation and treatment with antipsychotics for 3 weeks, long after the sertraline was discontinued, before his symptoms fully resolved. He has not taken any psychiatric medications since that time. Vital signs are within normal limits. Physical examination reveals no abnormalities. Serum chemistry panel, complete blood count, and thyroid-stimulating hormone (TSH) levels are within normal reference ranges. Which of the following is the most appropriate next step in the pharmacologic management of this patient's current symptoms?

  1. A
    Add lurasidone
  2. Add lithiumAnswer
  3. C
    Add citalopram
  4. D
    Add quetiapine
  5. E
    Obtain a serum free thyroxine (T4) level

Answer

The most appropriate next step is to add lithium, as it effectively treats bipolar depression without interacting with the patient's carbamazepine regimen.
This patient is experiencing an acute depressive episode in the context of Bipolar I disorder. His past manic episode (grandiosity, decreased sleep, pressured speech, hospitalization) emerged during SSRI treatment but persisted fully syndromal well beyond the physiological effect of the drug, confirming a Bipolar I diagnosis. First-line treatments for bipolar depression include lithium, lamotrigine, quetiapine, and lurasidone. However, this patient is taking carbamazepine, a potent inducer of several cytochrome P450 enzymes (particularly CYP3A4). Lithium is the most appropriate choice because it undergoes direct renal excretion and has no clinically significant pharmacokinetic interactions with hepatic CYP450 inducers.

Step-by-Step Solution

1
Diagnose the patient's underlying psychiatric condition based on past history.
Bipolar I Disorder.
The patient experienced a full manic episode during SSRI treatment that persisted at a fully syndromal level well beyond the physiological effect of the drug (requiring 3 weeks of inpatient antipsychotic treatment). According to DSM-5, this confirms Bipolar I Disorder.
2
Identify the current clinical episode.
Acute bipolar depression.
The patient presents with a 6-week history of depressed mood, anhedonia, hypersomnia, and weight gain.
3
Determine appropriate first-line treatments for acute bipolar depression.
Lithium, quetiapine, lurasidone, or lamotrigine.
These agents have demonstrated efficacy in treating the depressive phase of bipolar disorder without high risks of inducing mania.
4
Evaluate pharmacokinetic interactions with the patient's existing medication (carbamazepine).
Carbamazepine is a potent inducer of hepatic CYP3A4.
Quetiapine and lurasidone are heavily metabolized by CYP3A4. Their serum levels will be drastically reduced by carbamazepine (lurasidone is explicitly contraindicated). Lithium is renally cleared and bypasses the hepatic CYP450 system entirely, making it the safest and most effective choice.

Key Concept

Pharmacologic management of acute bipolar depression requires navigating drug-drug interactions; lithium is renally cleared and unaffected by potent hepatic CYP450 inducers like carbamazepine, unlike lurasidone or quetiapine.
Estimated Time:2m 0s
Rate this question

Topics

Bipolar and Related Disorders

More questions from this topic