Function

• Effexor affects the way the human body absorbs serotonin and it also works on the body's norepinephrine system. Most antidepressants work on one or the other, but not both.
  
  

Effects

• Side effects are usually considered to be dose-related. These effects present themselves or worsen as the patient dosage increases.
  
  

Common Side Effects

• Some of the more commonly reported side effects have been nervousness, sexual problems, nausea, weakness, sweating, sleepiness, headache, constipation and loss of appetite.
  
  

Severe Side Effects

• More severe side effects include those that occur as a result of allergic reaction such as difficulty breathing, swelling of the mouth, rash or hives. Bizarre behavior, confusion and chest pain have also been reported with Effexor use.
  
  

Warning

• Some of the severe side effects are considered life-threatening and patients experiencing these effects on Effexor should seek immediate medical help.