i have to add, that the lowest dose of lopressor that I have seen in the hospital where I work is 25mg. But that's the hospital and my pts are more acute. I don't know if there is a lower dosage than 25mg. So 0.5,mg i'm assuming that's what you meant, would be a tiny piece of that 25mg tab because .5mg is 1/2 of 1mg. If you meant 5mgs, well then, that would be 1/5th of the 25mg tab. I don't know any Doctor that would tell you to break a pill like that.