Allergic drug reactions mechanisms

Drug reactions mediated by immune responses can have several different mechanisms. Thus, any of the four major types of hypersensitivity discussed earlier in this chapter (page 967) can be associated with allergic drug reactions ... 

Co-administration of beta-blockers has been associated with an increased risk of severe allergic drug reactions and reduces the effect of adrenaline in the immediate treatment of anaphylactic shock. The mechanism involves changes in the regulation of anaphylactic mediators (281). 

Girard JP, Cattin S, Cuevas M (1976) Immunological mechanisms and diagnosis tests in allergic drug reactions. Ann Clin Res 8 74... 

Several workers have attempted to classify allergic drug reactions in terms of their underlying immunological mechanisms. Such a classification presupposes knowledge of their immunopathogenesis, and there are at present very few cutaneous drug reactions for which this is understood (Schulz 1972, 1974) ... 

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). 

The indications for Hi-antihistaminics are derived from their mechanism of action all conditions in which a histamine release, mainly as sequel of an allergic reaction (bronchial asthma, hey fever, urticaria, allergic reactions to food or drugs), dominates the clinical symptoms. They can be used pro-phylactically or in acute situations, even by intravenous application. 

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