Venlafaxine or Effexor affects various neuro chemicals in the body which are responsible for nervous system regulation. It inhibits specifically norepinephrine and serotonin reuptake, and also weakly inhibits dopamine reuptake. The net result is more neuro chemicals circulating in the nervous system. Venlafaxine or Effexor is generally well tolerated - nausea, headache, anxiety, nervousness, sweating, dizziness, insomnia, and drowsiness have been reported. Sexual dysfunction and weight loss may occur and can be problematic for the person experiencing this side effect.
Some people have a modest increase is diastolic blood pressure.
These effects seem to be dose related, and an adjustment in dose may solve the problem, otherwise stopping the drug may be needed. Venlafaxine or Effexor should not be combined with another class of antidepressant drugs known as monoamine oxidase inhibitors - MAOI's. The relevant product monographs must be regarded as the appropriate sources of prescribing information.