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by virtue of their nature, is to form a more viscous quasi-solid with the ingredients thus holding the mass in shape. |
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Liquid excipients are used where solvent action on the ingredients is warranted thus producing a mixture sufficiently adhesive to enable the formation of a mass. |
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Dry, also referred to as absorbent excipients, provide an increase in solidity when combined with the above two categories, enhancing the fluidity of the materials while forming them into their respective dosage forms. Dry excipients employed in the past, and even today, include magnesium carbonate/stearate, calcium phosphate, powdered acacia, kaolin, soap, cocoa butter, bread crumb, flour, powdered liquorice root, etc. |
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All dosage forms, conventional, nonconventional, past (cachets, pills), present (tablets, capsules), and future require inert materials as diluent excipients. Besides acting as bulking agents, i.e., fillers, the excipients in common use today often have ancillary functions such as binder action (sugar, pregelatinized starch), disintegration activity (microcrystalline cellulose, starch), or dissolution/release rate modifiers (polymers) particularly in the development and fabrication of pharmaceuticals/galenicals. |
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A. General Characteristics |
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The excipient must meet certain basic criteria for satisfactory performance in a final dosage form regardless of its physical and chemical functional characteristics. They MUST |
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be unreactive with the drug substance(s); |
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have no effect on the functions of other excipients; |
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not interfere with the bioavailability of the active material nor influence the dissolution of the product; |
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have no pharmaceutical and/or physiological activity; |
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not promote nor contribute the physical properties, such as segregation of the granulation power blend, and should be able to be milled, if required, to match the particle size distribution of the active ingredient; |
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have consistent and stable chemical and physical characteristics and properties from batch to batch and ideally between suppliers; |
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be colorless or nearly so; and |
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not support microbiological growth in the product nor contribute to microbiological load. |
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Chemically, modern solid dosage form excipients fall into two categories (Table 1): |
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carbohydrates and modified carbohydrate excipients, and |
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