A 45-year-old man with a confirmed diagnosis of pheochromocytoma (elevated plasma free metanephrines and adrenal mass on imaging) is deemed unfit for surgery due to severe comorbidities. Which drug is the preferred long-term medical management agent?

Explanation

## Long-Term Medical Management of Pheochromocytoma **Key Point:** Phenoxybenzamine remains the gold standard for sustained, long-term alpha-blockade in patients with pheochromocytoma who are not surgical candidates or awaiting surgery. ### Indications for Medical Management - Unfit for surgery (severe cardiac, pulmonary, or metabolic comorbidities) - Metastatic pheochromocytoma (malignant phenotype) - Awaiting surgery (preoperative preparation) - Recurrent or familial pheochromocytoma ### Comparison of Antihypertensive Agents in Pheochromocytoma | Agent | Mechanism | Duration | Onset | Role in Pheo | |-------|-----------|----------|-------|---------------| | **Phenoxybenzamine** | Non-competitive α-blocker | 12–24 hrs | Slow (days) | **First-line long-term** | | **Doxazosin** | Competitive α-1 blocker | 12–24 hrs | Moderate | Alternative if pheno unavailable | | **Labetalol** | α + β blocker (mixed) | 4–6 hrs | Moderate | Short-term/acute; NOT long-term | | **Esmolol** | β-1 selective blocker | 10 min | Very rapid | ICU/acute crisis only; never monotherapy | **High-Yield:** Phenoxybenzamine's **irreversible, non-competitive binding** allows sustained BP control even during catecholamine surges, making it superior to competitive blockers (doxazosin) for chronic management. ### Why Phenoxybenzamine for Long-Term Use? 1. **Sustained effect** → once or twice daily dosing (12–24 hour half-life) 2. **Catecholamine-independent** → blockade persists regardless of hormone levels 3. **Prevents hypertensive crises** → critical in unfit patients who cannot undergo surgery 4. **Proven long-term safety** → decades of clinical experience **Clinical Pearl:** In long-term phenoxybenzamine therapy, patients develop tolerance to tachycardia and postural hypotension. Salt loading and judicious beta-blocker use (after alpha-blockade) maintain hemodynamic stability. **Warning:** Doxazosin (competitive α-1 blocker) is an acceptable alternative if phenoxybenzamine is unavailable or poorly tolerated, but it is inferior because catecholamine surges can overcome its blockade.