Jane is a 42-year-old woman who was suffering from clinical depression. She was prescribed venlafaxine to treat her depression. She started to be agitated, had difficulties in breathing, had an elevated heart rate, and had tendencies of suicide. After experiencing these symptoms for six weeks, she visited her clinic. Her doctor increased the dose of venlafaxine. Despite this increase, her mood still did not improve and her mental condition, along with her fatigue, breathing difficulties and agitation worsened.
Jane’s symptoms were the side effects of venlafaxine. To find out whether venlafaxine was the cause, her doctors ordered a pharmacogenetic test. Through the pharmacogenetic test, they found out that Jane was a poor metabolizer of venlafaxine. So the doctor took Jane off of venlafaxine and switched her to an alternative antidepressant drug that the pharmacogenetic test predicted to work for her. Over time, her agitation, difficulty breathing, high heart rate and suicidal tendencies went away.
Wijnen, P.A. et al. (2009) Depressive effect of an antidepressant: therapeutic failure of venlafaxine in a case lacking CYP2D6 activity. Ann Clin Biochem 46, 527-30.