A wide range of drugs can cause immune mediated neutropenia. However, these idiosyncratic reactions only occur in a small number of patients. There are several mechanisms for drug induced antibody mediated neutropenia. One established mechanism occurs when membrane glycoproteins bind to the drug to form a hapten. This causes the formation of antibodies which only bind to granulocytes in the presence of the drug. Quinine, and its stereoisomer quinidine, is known to cause drug dependent antibody formation via this hapten mechanism.