Mood Disorders — Treatment of Bipolar II Depression
A 32-year-old man with bipolar II disorder has had 3 weeks of low mood, anhedonia, poor sleep and reduced concentration. He continues to work, has no suicidal ideation or psychotic features, and has no current hypomanic symptoms. He takes no psychotropic medication. His hypertension is controlled on lisinopril, and renal function is normal. Which of the following is the most appropriate management?
- A.Fluoxetine monotherapy
- B.Replace lisinopril with amlodipine
- C.Lamotrigine with slow dose titrationCorrect
- D.Electroconvulsive therapy
Explanation
A depressive episode in a patient with established bipolar II disorder is treated as bipolar depression, not unipolar depression. The aim is to lift mood without inducing hypomania or rapid cycling, so a mood-stabilising agent with antidepressant efficacy is chosen. Lamotrigine fits: it is effective against depressive relapse, has little tendency to provoke mood elevation, and is weight neutral. It must be started at 25 mg daily and increased gradually over about 6 weeks, because rapid titration raises the risk of Stevens-Johnson syndrome. Quetiapine is the only first-line agent for acute bipolar II depression in CANMAT/ISBD guidance; lamotrigine is a recommended second-line option, particularly useful for preventing depressive relapse. Antidepressant monotherapy such as fluoxetine is avoided because it can trigger hypomania and does not protect against future mood episodes. Lithium is effective, but angiotensin-converting enzyme inhibitors reduce its renal clearance and can produce toxicity, which is relevant in this man. Lisinopril does not cause depression, so changing it would not treat the episode. Electroconvulsive therapy is reserved for severe, psychotic, suicidal or treatment-resistant depression. Valproate co-prescription halves the required lamotrigine dose and is easily overlooked.
Why each option
- A.
- Antidepressant monotherapy in bipolar disorder risks a switch into hypomania or rapid cycling and offers no protection against future mood episodes.
- B.
- Lisinopril is not a recognised cause of depression; it matters only because it would raise lithium levels if lithium were chosen.
- C.
- Correct. Lamotrigine treats and prevents bipolar depression without provoking hypomania, but it needs slow titration to limit the risk of serious rash.
- D.
- Electroconvulsive therapy is kept for severe, psychotic, suicidal or refractory bipolar depression, none of which applies to this functioning outpatient.
Reference: CANMAT/ISBD Guidelines for the Management of Patients with Bipolar Disorder (Yatham et al., Bipolar Disord 2018); NICE CG185 Bipolar disorder: assessment and management (updated 2023)
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