Reaction, allergic decomposition

SAFETY PROFILE Compounds containing the isocyanate radical -NCO. Derivatives of isocyanic acid (cyanic acid). Usually the term refers to a diisocyanate. Inorganic isocyanates are only slightly toxic. Organic isocyanates (diisocy anates) can cause local irritation and allergic reactions. When heated to decomposition they emit toxic fumes of NO.. 

CAUTION DCC may cause severe allergic reactions to sensitive persons and the use of disposable gloves is recommended. Avoid all contact with the skin or mucosa. Wash immediately with acetone after any contact. In order to prevent DCC contamination of the balances, transfer DCC in the fume hood over disposable paper into a tared vial. Reweigh the vial with DCC and add dichloromethane to obtain a 1M solution. Prepare enough DCC reagent for the entire synthesis. Do not pipet the DCC solution by mouth. Violent decomposition may occur when either HOAt or HOBt are dried at elevated temperatures. 

As outlined by de Weck (1971) in one of his basic contributions to our understanding of drug reactions, the ability of a simple chemical to induce an immune response, and consequently allergic reactions, rests on its ability to form those macromolecular conjugates in vivo or on the presence in the final pharmaceutical preparation of substances with chemical reactivity towards body constituents. For this to occur, it is either necessary that the vitamins possess some intrinsic chemical reactivity, contain some reactive decomposition product or byproduct, or that a reactive species is metabolically created in vivo (the reactive metabolite). 

The complement system can also be activated without a preceding inunune reaction, and activated complement components (C3a, C5a) can induce histamine liberation and allergoid reactions. Accordingly, the clinical pictures described as allergic reactions to vitamins, and especially the anaphylactoid reactions after administration of vitamin B, should be attributed to an allergoid reaction until the presence of vitamin-specific antibodies has been unequivocally demonstrated. There have been no detailed investigations, so far, of the direct mast cell degranulating ability of vitamins. Therefore, it is not yet possible to come to any definite conclusion on this point. Reactions can also be caused by the vehicles used as well as by possible decomposition products. 

For safety reasons, it might be necessary to provide a special product form, mainly to minimize particle attrition and dust generation (see example for SPC in Ref. 90), but also to prevent allergic reactions (see example for KMPS in Ref. 91). In some cases, the physical properties of the bleach component itself reqnire special attention, for example, to reduce the risk of self-decomposition (see Section 16.3.5). 

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