I had been receiving this prescription by the manufacturer Lupin Pharm. Then my provided switched to Sandoz. Since then, I have noticed that I waking up with headaches and my blood pressure does not seem t be as under control as it was I found some of the Lupin and switched back to them for a couple of weeks and the problems went away. Unfortunately, I ran out and had to go back to the Sandoz and the headaches, etc. are back. Have you ever heard of this? What could be causing it?