Metabolism of Inderal verses Atenalol

  Dear Doctor;
  Is it true that Inderal is metabolized to a much greater extent in the liver than Atenalol?
  In a liver whose capacity is reduced or a shunt around the liver exists could this lead to much higher concentrations of Inderal in the systemic circulation
  causeing near syncope, darkening of the vision and bradycardia?
  Should this first statement be true and have taken place, why would Ativan greatly reduce the symptoms of the apparent near syncope? Does Ativan reduce the oxygen demand of the brain?
  Or could it maybe help block the Inderal from the beta 2 receptor sites?
  
  Thanks.
  Bob Muller

[CCF Cardio MD-SGM]

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Dear Mr. Muller,
You are correct that Inderal(propranolol) undergoes more hepatic (liver)metabolism than does
atenolol.     For this reason, propranolol should be used cautiously, if at all, in persons with advanced liver disease.  Atenolol, on the other hand, undergoes little to no hepatic metabolism, and is relatively safe for use in the setting if liver dysfunction.  
The symptoms you discussed, such as syncope and bradycardia, could well have been a manifestation of beta-blocker (propranolol) toxicity.  They could also be due to a variety of other causes, however, and a blood test indicating toxic levels of propranolol would be helpful in establishing any direct connection between these two events.  
Ativan has no effect on beta receptors and does not play an important role in cerebral oxygen utilization or blood flow.  Ativan should not reduce the symptoms of syncope due to beta blocker toxicity.  Certain types of anxiety disorders and panic disorders that are associated with syncope/ near syncope/ dizziness may respond to ativan, however.  
Information in the Heart Forum is for general purposes.  Specific diagnoses and therapies can only be provided by your personal physician.