Pheochromocytoma Treatment

Alpha-Adrenergic Blockade

• First-line therapy used to minimize complications prior to surgery

Phenoxybenzamine

• Action: Powerful irreversible alpha-adrenergic blocker of the alpha receptors in the smooth muscles
• Effects: Oral administration results in an onset of action w/in a few hr & persists for up to 3-4 days
  
  • Used to control the hypertension caused by excessive catecholamine release by pheochromocytoma

Selective Alpha₁-Antagonists

• Eg Doxazosin
• Action: Selective blockade of alpha₁-adrenoreceptors
• Effects: Limited use in pheochromocytoma, Phenoxybenzamine is more effective
• May be used to treat individual paroxysms
• May also may be used to treat hypertension while pheochromocytoma workup is ongoing
  
  • Better tolerated than Phenoxybenzamine
  • Prevent serious pressor crisis if pheochromocytoma is present

Beta-Blockers

• Eg Propranolol, Atenolol
• Administer only after alpha blockade has been induced
  
  • W/o alpha blockade paradox increase in BP may occur

• Action: Competitive antagonists of catecholamines at beta-adrenergic receptors
• Effects: Used to treat tachycardia that may develop w/ alpha blockade
  
  • Assist in preventing catecholamine-induced arrhythmias

• Low doses are usually sufficient

Calcium Channel Blockers

• Eg Nifedipine, Amlodipine
• Used as add-on treatment to alpha-adrenergic receptor blockers to further improve cardiovascular function peri-operatively
• Action: Blocks slow calcium channels to prevent calcium ion flow into the cell
• Effects: Vasodilatation, reduced afterload, peripheral resistance & blood pressure

Metirosine (Metyrosine)

• Action: Inhibits tyrosine hydroxylase which inhibits synthesis of catecholamines by the tumor
• Effects: Simplifies chronic management
• Should be used if other agents are ineffective or when tumor destruction will be marked