I take 50 mg of Toprol and 300/25 of Avalide. All the Toprol does for me is keep my pulse at 60 and the Avalide keeps my blood pressure around 137/85.

I have been on high blood pressure for 7 years and have tried about 10-12 blood pressure meds, most in the last 5 months. On New Years Eve I ended up in the hosipital after I passed out a the Drs office. They found I had low potassium caused by diruetics. Since I have been out I have been thru a lot meds and have had a slew of tests to see why my blood pressure is high. Since I have beem on Avalide and Toprol it seems to be manageable. To answer your question yes meds will stop working or cause an adverse reaction when something changes in the body. Very few people on high blood pressure or cholerestrol meds will stay on the same meds.