As an anti-estrogen it is best to use it while on a cycle to reduce bloat, gyno and other estrogen related sides. And it is also useful after a cycle in conjunction with clomid as a gainskeeper formula. And while off cycle it is also useful to help keep your endogenous testosterone from converting to estrogen.
The only sides I know of are not related to the liver or kidneys, but to cholesterol. It will reduce your estrogen levels, and estrogen has many beneficial effects on the body, of which the most important have to do with cholesterol.