Yes I've been taking Metoprolol succinate. Metoprolol succinate is an extended-release version of metoprolol, so it remains in your bloodstream for a longer time. Metoprolol tartrate is an immediate-release version of metoprolol.

I started 12.5 mg once daily for over a year now for a fast resting heart rate, and yes I am having growing problems with muscle cramps, spasms, stiffness and joint pain which makes no sense to me. It has caused a lot of anxiety and making it difficult to walk. I contacted my cardiologist and PCP and both stated definitely not to quit, reduce the dosage until something else could be prescribed.

Unfortunately, I lost my medical insurance and could not make an office apt to see the cardiologist or PCP for a different prescription naturally they would not prescribe another medication without seeing me.

The muscle spasms, cramps and stiffness are definitely a side effect. On some websites it's considered "less common" but it is listed (also on the Mayo Clinic website)

After significant research I found that metoprolol has an "anti-anxiety" agent which relaxes and lowers the heart rate. This can make it difficult for some people to quit cold turkey because after long term use the body can build a dependence on it so after consulting your doctor, reducing the dosage until another medication is prescribed makes sense for some.

Also, there are some people who are sensitive to Beta Blockers, I'm also one of them. I have searched and searched to understand what specifically in metoprolol causes this condition but can't find anything that explains it.There may possibly be vitamin or supplement that may help?