A 28-year-old man with bipolar II disorder presents with a depressive episode. He has a history of poor tolerability to lithium (tremor, polyuria). Which is the drug of choice for mood stabilization in this patient?

Explanation

## First-Line Mood Stabilizer in Bipolar II Depression with Lithium Intolerance **Key Point:** Lamotrigine is the drug of choice for bipolar II depression, especially when lithium is contraindicated or poorly tolerated. It is the only mood stabilizer with superior efficacy in bipolar depression over mania. **High-Yield:** Lamotrigine's unique profile in bipolar II disorder: - **Efficacy:** Proven benefit in bipolar depression; minimal efficacy in acute mania - **Indication:** Bipolar II disorder and bipolar depression - **Tolerability:** No tremor, no polyuria, no renal/thyroid monitoring required - **Dosing:** Slow titration required (25 mg → 50 mg → 100 mg → 200 mg over 4–6 weeks) due to risk of rash - **Mechanism:** Inhibits glutamate and aspartate release; stabilizes mood via GABA enhancement ## Comparison of Mood Stabilizers in Bipolar II Disorder | Feature | Lamotrigine | Lithium | Valproate | Topiramate | |---------|-------------|---------|-----------|------------| | **Efficacy in depression** | **Excellent** | Good | Moderate | Limited | | **Efficacy in mania** | Minimal | Excellent | Excellent | Moderate | | **Best for bipolar II** | **Yes** | Bipolar I | Bipolar I | Off-label | | **Tremor/polyuria** | No | **Yes** | No | No | | **Renal monitoring** | No | **Yes** | No | No | | **Slow titration needed** | **Yes (rash risk)** | No | No | No | | **Pregnancy category** | C | D | D | C | **Clinical Pearl:** Lamotrigine must be titrated slowly to minimize the risk of Stevens–Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN), especially in the first 8 weeks. Rapid titration or concurrent use with valproate (which inhibits lamotrigine metabolism) increases rash risk. **Warning:** ~~Lamotrigine is effective in acute mania~~ — Lamotrigine has minimal efficacy in acute mania and should not be used as monotherapy for manic episodes. It is reserved for bipolar depression and maintenance in bipolar II disorder. **Mnemonic:** **LAM-Depression** — **LAM**otrigine for **Depression** in bipolar disorder. ## Titration Schedule for Lamotrigine ``` Week 1–2: 25 mg daily Week 3–4: 50 mg daily Week 5–6: 100 mg daily Week 7+: 200 mg daily (maintenance) ``` If concurrent valproate use, halve all doses (valproate inhibits lamotrigine glucuronidation) [cite:KD Tripathi 8e Ch 12].