Thrombocytopenia allergic drug reaction

Blood dyscrasias, mostly dose independent, are among the most important allergic-type adverse reactions to drugs. Aplastic anemia is a serious but rare (presumably) idiosyncratic reaction. It has been reported in association with chloramphenicol, quinacrine, phenylbutazone, mephenytoin, gold compounds, and potassium chlorate. Hemolytic anemia, thrombocytopenia, and agranulocytosis may result from an unusual, acquired sensitivity to a variety of widely used drugs including aminopyrine, phenylbutazone, phenothiazines, propylthiouracil, diphenylhydantoin, penicillins, chloramphenicol, sulfisoxazole, and tolbutamide. 

Adverse effects are frequent. Patients may experience gastrointestinal upset, and dose-related impairment of taste is common. Thrombocytopenia is frequent but resolves when the drug is withdrawn unless it indicates the more serious aplastic anaemia which may also occur. Allergic reactions (rashes, fever) tend to occur during the early stages of treatment. Proteinuria, if it is heavy, is a reason for stopping penicillamine for it may herald the development of the nephrotic syndrome. 

The main varieties of adverse effects attributed to cimetidine relate to its antiandrogenic properties and its actions in sufficient concentrations on the central nervous system. There is also a spectrum of drug interactions, mainly attributable to inhibition of hepatic CYP isoforms, but they only have clinical consequences under special circumstances. Occasional adverse effects, which are generally minor, include bradycardia and conduction defects, thrombocytopenia, neutropenia, interstitial nephritis, mild hepatic dysfunction, and headache. Intestinal infection due to loss of the gastric acid barrier also occurs, and myalgia, fever, monoamine oxidase-Uke interactions, and neuropathies have been well documented occasionally. Allergic reactions, such as bronchospasm, have rarely been described. Anaphylaxis with recurrence on rechallenge is on record, as are asthma and skin effects. 

Acetaminophen usually is well tolerated at recommended therapeutic doses. Rash and other allergic reactions occur occasionally. The rash usually is erythematous or urticarial, but sometimes it is more serious and may be accompanied by drug fever and mucosal lesions. Patients who show hypersensitivity reactions to the salicylates only rarely exhibit sensitivity to acetaminophen. The use of acetaminophen has been associated anecdotally with neutropenia, thrombocytopenia, and pancytopenia. 

The main side-effect of heparin is bleeding. Because it has a shrrn duration of action (4-6 hours), bleeding can usually be controlled by Slopping the drug administration. If necessary, heparin can be neutralized by the intravenous injection of protamine, a basic jreplide ihai combines with the acidic heparin. Heparin occasionally causes allergic reactions and thrombocytopenia,... 

Some of these drugs, mainly pyrazolone derivatives, may cause agranulocytosis or thrombocytopenia, or both, (type II reactions), but only in rare, or extremely rare, situations (Baumgartner et al. 1982). Digitalis and also benzodiazepines induce adverse reactions only exceptionally by an allergic mechanism (Streit 1979). 

The unambiguous demonstration, in presumptive allergic reactions, of immunochemical specificity determined by drug-derived haptenic structures, is absent in the majority of cases, with the exception of some instances of contact allergic dermatitis induced by antifungal agents applied topically. In this chapter immunochemical specificity is discussed also in relation to the antibodies responsible for quinine-induced thrombocytopenia and levamisole-induced anti-leucocyte antibodies in agranulocytosis. 

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