This situation has gone on way too long and it will take both parties to reconcile the marriage and the relationship. Should this marriage be saved? I think so if there was love to start. Apparently the counseling isn't helping, which tells me either the couple isn't willing to try or the counselor is not appropriate for this situation.
My first marriage was pretty awful and I stood it for only 2 1/2 years. My second marriage has been good and we have been working at it for 32 years. Yes, I did say work! Even the best of relationships take work. I call it taking out the "garbage" on a regular basis. If it piles up then it gets harder and harder to remove it. One cannot simply stand by and let their partner denigrate or snipe at them. Even now when my hubby gets grumpy and makes a nasty comment, I call him on it immediately. You cannot let these things go. You lose respect for yourself and your spouse. It is all part of keeping a relationship "honest".
Speaking of keeping things honest...adultry has already been committed in this man's heart. He should remove himself from this extra-marital relationship immediately before it becomes more involved than it is already. He needs to do some praying and/or soul searching.
My parents stayed together for the "sake of us children". It would have been much better if they had tried to either fix their marriage or get out. What kind of lesson are these kids learning with their mom on drugs (prescribed or not doesn't matter) and their dad's eye wandering?
My suggestion is that the couple both read Dr. Mercola's web site, www.mercola.com, and take the metabolic typing survey. Start eating healthy foods and get weaned off meds. This healthy eating will be better for the kids too. The suggestion above of a good cleansing is a really great idea-for both partners.
My next suggestion is for the couple to both read a book called "Children the Challenge" by Dreikurs. It is aimed at parents raising children but is very helpful for all relationships.
The wife needs something productive to do with her life. I'd suggest she get out of herself and help someone else. Volunteer work would be good for her and her community/children.