I was on Toprol XL for an irregular heart beat. Then I switched t...

I was on Toprol XL for an irregular heart beat. Then I switched to the generic Metoprolol Succinate ER. I had no problems until they started being made by a different manufacturer. Not only did they look entirely different, but they did not treat the symptoms. When I called the manufacturer they said that it was very unlikely there was a problem since they were regulated by the FDA. I recently found out that one manufacturer was cited by the FDA in August of 2008 for failure to comply with regulations. It was brought to their attention by consumer complaints. I went back on the the name brand for a while but when I could no longer afford them, I went back on the generic. I had no problems then but I just went back to get a refill and was told the manufacturer was no longer making the generic and only the name brand was available. The generic was ordered from a different manufacturer and was on back-order, so I had to go back on the name brand. I would like to know what is going on with this drug. why have there been so many complaints when consumers were switched to a different manufacturer and why have at least two manufacturers stopped making it?