Equivalence of left R module category and the opposite of the right R module category

Question

I was wondering if the left $R$ module category is equivalent to the opposite category of the right $R$ module category. All that I know is that the category of left modules over $R$ is equivalent to the category of right modules over the opposite ring $R^{op}$. But I can't state whether there is the equivalence to the opposite category or not. Anyone help?