Cyclophosphamide is a widely applied agent in treatment of systemic lupus erythematosus. As an alkylating agent, cyclophosphamide is able to induce several side effects, including thinned hair, loss of appetite, nausea, vomiting, infection, myelosuppression, etc. However, the remarkable variability of the reactions to the drug -- the incidence of side effect or the outcome of the treatment -- has been observed among patients. Cyclophosphamide is a pro-drug, which require some enzymes in the liver to transform it into an active chemical to arouse alkylating function. And then it undergoes a series of detoxification steps catalyzed by the specific metabolic enzymes. This study is designed to explore the genetic variation among individuals in the key processes of the activation and elimination of cyclophosphamide in order to find out whether these genetic factors are associated to the side effects or efficacy. The further understanding into the factors concerning on the drug might imply possible solution to minimize the incidence of side effects in patients of systemic lupus erythematosus.
