Patients should discuss with their physician the benefits and risks of taking beta blockers if they have been diagnosed with any of the following conditions:

• Bradycardia (abnormally slow heart rates). Beta blockers can further reduce the heart rates of these patients to dangerously low levels, increasing the risk of heart failure, angina and loss of consciousness.
  
  
• Heart block (partial or complete loss of electrical communication between the chambers of the heart).
  
  
• Asthma, emphysema or bronchitis. Beta blockers can cause constriction of tiny air tubes (bronchioles), possibly worsening these lung diseases.
  
  
• Chronic obstructive pulmonary disease (COPD). Beta blockers may aggravate this condition and should be avoided in patients with severe COPD. Among patients with mild to moderate disease, they should be used at low doses or possibly in combination with another medication.
  
  
• Peripheral vascular disease. Beta blockers may cause worsening of symptoms among patients with vascular disease, including cold extremities and, in some cases, tissue death and gangrene.
  
  
• Kidney or liver disease. These conditions may cause beta blockers to be removed from the body at a slower rate, increasing the risk of overdose and/or side effects.
  
  
• Diabetes. Beta blockers may mask the symptoms of hypoglycemia (low blood sugar) and slow or impair the body’s recovery from an episode of insulin-induced hypoglycemia.
  
  
• Insulin resistance and metabolic syndrome, two known risk factors for heart attack. Beta blockers may increase blood sugar (glucose) levels.

In addition, beta blockers may make the following disorders worse:

• Raynaud syndrome. A painful condition caused by the temporary constriction of the small arteries in the hands and feet.
  
  
• Psoriasis. A chronic skin condition characterized by red patches with white scales.
  
  
• Clinical depression or a history of this condition.
  
  
• Myasthenia gravis. A progressive weakness of voluntary muscles.