Effexor extended-release is a capsule that has to be used through oral administration. Effexor extended-release is a capsule that has to be used through oral administration. Effexor affects chemicals in the brain called serotonin and norepinephrine reuptake inhibitors. Stopping Venlafaxine too quickly may cause serious side effects or your condition may worsen. You feel the full effect of Effexor.