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CHEMICAL INCOMPATIBILITY, It may be as a result of chemical, interaction between the ingredients of the prescription and a toxic or, inactive product may be formed., , Chemical incompatibilities often occur due to, oxidation reduction, acid base hydrolysis or combination reactions., These reactions may be noticed buy precipitation, effervescences, decomposition, colour change or by explosion., , S) s

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It is of two types, , Tolerated - The chemical interaction can be minimized by changing, the order of mixing or mixing the solution in dilute forms but no, alteration is made in the formulation., , Adjusted - The chemical interaction can be prevented by addition or, substitution of one of the reacting ingredients of the prescription with, another of equal therapeutic value., , e.g. caffeine citrate can be substituted with caffeine in sodium, salicylate and caffeine citrate mixture.

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CHEMICAL INCOMPATIBILITIES : TYPES, , Precipitate yielding interactions, , © The precipitates so formed may be diffusible or, indiffusible. The method A or B is followed in, dispensing the prescription yielding diffusible and, indiffusible precipitates respectively., Method A — Diffusible precipitate, , Method B — Indiffusible precipitate, , 1 The preparation should contain a thickening agent if, the precipitate is non-diffusible., , , , Method A:, , oThis method is suitable for diffusible, precipitates and the following steps are, carried out., , 4 Divide the vehicle into two portions., « Dissolve the reactants in separate portions, , and mix the two portions slowly by, adding one into other with rapid stirring.

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Method B , This method is followed for indiffusible precipitate forming solids., Divide the vehicle into two equal portions., , Dissolve one of the reacting substance in one portion., , Weigh a suitable quantity of compound tragacanth powder (2, gm /100 ml of finished product) & transfer ina mortar & use part of, second portion of vehicle to produce smooth mucilage., * Then add other reacting substances. Mix the two portions by, slowly adding one portion to other with rapid stirring.

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Examples of chemical incompatibilities and, methods of their correction, , Alkaloid incompatibility :, 1. Alkaloidal salts with alkaloid substances, , 2. Alkaloidal salts with soluble iodides, , 3. Alkaloidal salts with tannins, , 4. Alkaloid salts with salicylates, , 5. Alkaloid with soluble iodides and bromides., , ~ Soluble salicylates incompatibility:, © 1.Soluble salicylates with ferric salts, 2.Soluble salicylates with alkali bicarbonates, 3.Soluble salicylates and benzoates with acids., , Soluble iodides incompatibility:1.Oxidation of iodides with potassium chlorate, © 2.Oxidation of iodides with quinine sulphate.