A 38-year-old woman with a history of panic disorder presents to the clinic with recurrent episodes of palpitations, tremor, and a sense of impending doom lasting 20–30 minutes. Physical examination shows heart rate 110 bpm, blood pressure 145/92 mmHg, and mild diaphoresis during the episode. 24-hour urinary metanephrines and plasma free metanephrines are normal. Thyroid function tests are normal. What is the most appropriate next step in management?

Explanation

## Panic Disorder vs. Organic Catecholamine Excess: Diagnostic and Management Approach ### Clinical Differentiation | Feature | Panic Disorder | Pheochromocytoma | |---------|---|---| | **Metanephrines** | Normal | Elevated (>4× upper limit) | | **Duration** | 20–30 min (self-limited) | Hours to days | | **Triggers** | Psychological stress, anticipatory anxiety | Spontaneous, positional, Valsalva | | **Hypertension** | Episodic, during attacks | Sustained or paroxysmal | | **Diaphoresis pattern** | During anxiety | Profuse, spontaneous | | **Tremor** | Fine, anxiety-related | Coarse, catecholamine-driven | **Key Point:** Normal plasma metanephrines essentially exclude pheochromocytoma (sensitivity >99%). This patient's biochemistry rules out catecholamine excess. ### Why Panic Disorder Is the Diagnosis 1. **Biochemistry is normal:** Plasma metanephrines are the most sensitive screening test; normal values exclude pheochromocytoma 2. **Psychiatric history:** Known panic disorder with recurrent episodes fitting the diagnostic criteria (DSM-5) 3. **Episode characteristics:** 20–30 minute duration is typical of panic attacks; pheochromocytoma episodes usually last longer 4. **Thyroid excluded:** Normal TSH rules out hyperthyroidism **Clinical Pearl:** Panic disorder is one of the most common mimics of pheochromocytoma. The key discriminator is biochemistry—normal metanephrines = panic disorder until proven otherwise. ### Management of Panic Disorder **First-line:** Cognitive behavioral therapy (CBT) with or without pharmacotherapy **Pharmacotherapy options:** - **SSRIs** (sertraline, paroxetine, escitalopram) — first-line; take 2–4 weeks for full effect - **SNRIs** (venlafaxine) — alternative - **Benzodiazepines** (lorazepam) — short-term symptom relief only; avoid long-term due to dependence risk - **Beta-blockers** (propranolol) — manage somatic symptoms (palpitations, tremor) but do NOT treat the underlying anxiety disorder **High-Yield:** CBT is the gold standard and most effective long-term treatment; SSRIs address both panic and comorbid depression/anxiety. **Mnemonic:** **"SSRI-CBT"** — the two pillars of panic disorder management. **Tip:** In exam questions, if metanephrines are normal and panic disorder is in the history, the answer is always psychiatric intervention (CBT ± SSRI), not further organic workup.