The use of Effexor XR for children and teens has not been approved. In studies, the risk of suicidal thoughts and behavior increased for these age groups. Young adults may also be at increased risk. Individuals taking MAOIs (monoamine oxidase inhibitors), another antidepressant, should not use Effexor XR. Individuals using illegal drugs should not take Effexor XR.There are many other medications that may contraindicate the use of this drug and these should be discussed with your doctor.