As best you can, take this medication at the same time every day. For a long time I was taking only 150mg a day and didn't feel any benefits from the medication. However, when my psychiatrist increased my dose to 300mg a day, I could detect a significant improvement in mood. This is a relatively high dose for this medication and it can cause an increase in blood pressure. Fortunately this has not been an issue for me but might be something for others to take into consideration.
Also, I take the XR-capsules and I can tell a difference between the XR and non-XR.