Metoprolol is available in two forms, fast acting Metoprolol Tartrate
(Lopressor), and the time release Metoprolol Succinate
(Toprol XL). I used both, and found that side effects are similar; tiredness, weight gain, and a slow pulse. Side effects are more pronounced as the dosage is increased. I had dosages from 25mg to 200mg. daily. Other reported effects are loss of libido, tightness in the chest, itching, irregular breathing, and irregular heartbeat.