I no longer can take toprol (makes me feel like a zombie), but I used a Fibercon tablet each day when I did take toprol. I still use Fibercon daily because I have irritable bowel (constipation) and it works so much better for me than Metamucil (which gave me gas and bloating. Citrucel caused gas/bloating too). I sometimes use the store brands that have the same ingredients as Fibercon since they are a lot less expensive. Hope this helps.
I cannot think of any reason why you would not be able to. Other therapies for constipation include stool softners such as senna or colace. Drinking plenty of fluids (if you are dehydrated) can also help.