Like all medications, taking abatacept carries some risk of side effects, which must be balanced with the potential benefits. In general, the risk of joint damage and permanent disability (resulting from arthritis) is much greater than the risks of side effects from abatacept. When monitored properly the vast majority of side effects are rare, most improve over time and are reversible.
Firstly, abatacept can increase your risk of infections.
In rare cases, people may experience headaches, nausea, back pain and a rash while taking abatacept. If these symptoms become severe please consult your health-care provider.
Also in uncommon circumstances, abatacept can cause an allergic reaction during the infusion (flushing, itching, changes in heart rate and blood pressure, etc.). A health-care provider will monitor for this reaction during the infusion. For people taking the medication by injection, abatacept can in rare instances cause an injection site reaction (redness, pain and itching). Talk to your health-care provider if these symptoms become severe.