Chemistry Reference
In-Depth Information
CHAPTER 7
Excipients: Their Role in
Rational Formulation Design
7.1 Definitions and Classifications
Pharmaceutical agents are rarely single-component preparations, if only
because of the ubiquitous presence of residual water in all products. Two-
component aqueous mixtures can also be ruled out in practice. A liquid
solution that is to be freeze-dried to yield an acceptable solid dosage form
will therefore contain several components, some of them carried over from
downstream processing, e.g. chromatographic separations, while others
are added prior to freeze-drying, for specific purposes, such as processing
aids or for the stability enhancement of a dried product. The term
''excipient'', which does not occur in standard dictionaries, is now gener-
ally used indiscriminately to describe any substance(s) already present or
added to the solution of the bioactive component prior to freezing. In a
guide published by the International Pharmaceutical Excipients Council
(IPEC), the term ''excipient'' is defined as:
. . . substances, other than the active drug substance of a finished dosage
form, which have been appropriately evaluated for safety and are in-
cluded in a drug delivery system to either aid the processing of the drug
delivery system during its manufacture; protect; support; enhance stabil-
ity, bioavailability, or patient acceptability; assist in product identifica-
tion or enhance any other attributes of the overall safety and effectiveness
of the drug delivery system during storage or use.
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A less wordy definition appears in the Oxford Concise Medical Reference
Dictionary as''... asubstancethatiscombinedwithadrugtorenderit
suitable for administration; for example in the form of pills. Excipients
should have no pharmacological actions themselves''. There are, however,
indications that in certain situations, excipients do interact with the drug
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