Multiple Sclerosis (MS) is chronic, inflammatory, a neurologic disorder of the central nervous system (CNS). Although the exact mechanisms of MS have not been yet discovered some drugs are found helpful for its treatment. These drugs which are divided into the first line, second line and third-line therapies, have demonstrated to be helpful for MS patients based on immune basic of the disease. Previous studies have been indicated that deterioration of MS condition is associated with a stronger immune system. Most of these therapies impact on the immune system and immune cells including shifting immune cell populations toward a Th2 dominant population or suppression of the immune system so that auto-reactive immune cells cannot attack myelin sheath of neurons. Beside many beneficial effects of these drugs, some adverse effects (AE) have been reported in many experiments and clinical trials among patients suffering from MS. In this review, we conclude some AEs of beta interferon, mitoxantrone, natalizumab and fingolimod, reported in different papers and we continue the rest of the drugs in second part of our review article.