Blocks adrenalin. Metoprolol is a beta-blocker which blocks beta receptors in the heart and body. It is useful in blocking the effect of Adrenalin on the heart making it less likely for irregular heart beats such as pvc's to occur. Taking a long acting form of metoprolol (succinate) at night may allow for control of the pvc's all day and decreases fatigue a side effect that some people experience.
Pvcs. Largely depends on when the symptoms are more prevalent.