Adverse drug reactions allergic response mechanisms

Several types of adverse drug reactions do not easily fit into Cell and Coomb s classification scheme. These include most cutaneous hypersensitivity reactions (such as toxic epidermal necrolysis), immune-allergic hepatitis and hypersensitivity pneumonitis. Another difficulty is that allergic drug reactions can occur via more than one mechanism picryl chloride in mice induces both type 1 and type IV responses. Although other classification schemes have been proposed. Cell and Coomb s system remains the most widely utilized scheme [4-7]. 

In some drug reactions, several of these hypersensitivity responses may present simultaneously. Some adverse reactions to drugs may be mistakenly classified as allergic or immune when they are actually genetic deficiency states or are idiosyncratic and not mediated by immune mechanisms (eg, hemolysis due to primaquine in glucose-6-phosphate dehydrogenase deficiency, or aplastic anemia caused by chloramphenicol). 

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