ABSTRACT
Adverse Drug Reactions (ADRs) are common with recent estimates of 2–4 million persons/year suffering disabling or fatal injuries from prescription drugs. ADRs are defined by the World Health Organization as a noxious, unintended and undesired effect of a drug, which occurs at doses used in humans for prophylaxis, diagnosis or therapy. Immunologically-mediated ADRs begin with recognition of the drug as an antigen by the immune system. Drugs can be recognized by the immune system through a variety of pathways that can lead to immune activation. Most medications consist of small molecules that are not able to interact directly with receptors on immune cells to activate the immune system. Some small molecules form reactive intermediates during drug metabolism. Before they can be conjugated for detoxification, these drug metabolites can act as haptens which are commonly referred to as prohaptens. Some medications such as hormones, enzymes, vaccines and monoclonal antibodies, are macromolecules or peptides.
