A.  Multiple sclerosis (MS) is a disease of nervous system in which there occurs loss of myelin (the outer covering of nerve cells) due to an inflammatory process of unknown cause. The myelin is responsible for the rapid conduction of information from one part of nervous system to another. Therefore, with patchy loss of myelin in multiple sclerosis, the nervous tissue is not able to function properly (by transmitting and receiving information rapidly and correctly). Depending on the site of involvement in the nervous system, the symptoms vary. The course of the disease is highly unpredictable. The commonest form, called "relapsing and remitting" as the name suggests, shows sudden worsening followed by gradual recovery and then again worsening interspersed with variable time intervals. This occurs because the body has inherent capacity to heal the myelin loss and regenerate them. When multiple such areas in the nervous system get affected multiple times, the area appears “sclerosed” when seen microscopically using certain dyes, hence the name “Multiple sclerosis”. Recurrent attacks may however, leave behind permanent residual deficits and the recovery may be incomplete. Also, with recurrent and severe attacks, there may be additional loss of the nerve cells (in addition to the myelin) which may lead to persistent residual deficits. It is very difficult to predict how a patient will behave clinically after the diagnosis is made. Since, the cause of the disease is incompletely understood, there is yet no permanent cure for the disease. Acute attacks are usually treated with steroids. Beta interferons are given to prevent the future attacks and thereby reduce the chances of disability resulting from future attacks. Thus, these are preventive drugs. However, it is to be noted that these are not 100% preventive and patients may still experience clinical attacks while taking them. Further, these are injectables, have to be taken on regular basis for prolonged period of time and are costly. Some adverse effects like pain at the injection site, flu like symptoms etc are common. Some patients develop depression like symptoms also. They, on occasions, can also have effects on blood (decrease lymphocyte counts) and liver (increase liver enzymes). Safety data of these agents during pregnancy and lactation are sparse and generally these are not recommended during pregnancy (or in persons who want to have pregnancy). Despite these limitations, currently these are the best medicines that have been shown to have moderate efficacy in preventing further attacks of MS.