### Date : 2024-06-19 19:16 ### Topic : #internalmedicine #medicine ---- ### Alpha Blockers Used in Pheochromocytoma **Pheochromocytoma** is a rare tumor of the adrenal glands that produces excessive catecholamines (epinephrine and norepinephrine), leading to severe hypertension and other symptoms. Effective management includes the use of alpha blockers to control blood pressure and prevent hypertensive crises, particularly before surgical removal of the tumor. ### Commonly Used Alpha Blockers 1. **Phenoxybenzamine:** - **Class:** Non-selective, irreversible alpha-adrenergic antagonist. - **Mechanism of Action:** Blocks both alpha-1 and alpha-2 adrenergic receptors, leading to vasodilation and decreased blood pressure. - **Dosage:** Typically started at a low dose (e.g., 10 mg twice daily) and gradually increased based on blood pressure response and patient tolerance. - **Advantages:** Long-acting, providing consistent control of blood pressure. - **Side Effects:** Orthostatic hypotension, reflex tachycardia, nasal congestion, fatigue. 2. **Doxazosin, Prazosin, Terazosin:** - **Class:** Selective alpha-1 adrenergic antagonists. - **Mechanism of Action:** Selectively block alpha-1 receptors, resulting in vasodilation and reduced blood pressure without significantly affecting alpha-2 receptors. - **Dosage:** - **Doxazosin:** Often started at 1 mg daily and titrated up as needed. - **Prazosin:** Typically started at 1 mg two to three times daily and titrated up. - **Terazosin:** Often started at 1 mg daily and titrated up as needed. - **Advantages:** Shorter-acting than phenoxybenzamine, allowing for easier dose adjustments. - **Side Effects:** Orthostatic hypotension, dizziness, headache, fatigue. ### Example Case Study **Patient Profile:** - **Name:** Jee Hoon Ju - **Age:** 48 - **Occupation:** Engineer **Medical History:** - **Symptoms:** Episodes of severe headaches, palpitations, sweating, and hypertension. - **Diagnosis:** Confirmed pheochromocytoma via imaging (CT scan) and elevated plasma metanephrines. **Management:** 1. **Initial Treatment with Alpha Blockers:** - **Drug:** Phenoxybenzamine. - **Dosage:** Started at 10 mg twice daily and gradually increased to 20 mg twice daily over two weeks. - **Monitoring:** Blood pressure and heart rate closely monitored to adjust dosage. 2. **Preparation for Surgery:** - **Beta Blockers:** Added after adequate alpha blockade to control tachycardia (e.g., propranolol 10 mg three times daily). - **Hydration:** Ensured adequate fluid intake to prevent orthostatic hypotension. 3. **Surgical Removal:** - **Procedure:** Adrenalectomy performed to remove the pheochromocytoma. - **Postoperative Monitoring:** Blood pressure and catecholamine levels monitored to ensure no recurrence or residual tumor. ### Conclusion Phenoxybenzamine is the most commonly used alpha blocker in the management of pheochromocytoma due to its long-acting, non-selective properties. Selective alpha-1 blockers like doxazosin, prazosin, and terazosin are also used and can be advantageous for their shorter duration and ease of dose adjustment. Proper preoperative management with alpha blockers, followed by surgical removal of the tumor, is essential for optimal outcomes in patients with pheochromocytoma. Regular monitoring and careful dosage adjustments are crucial to prevent hypertensive crises and ensure patient safety.