What is the difference between an assay and an extemporaneous preparation?
Can an extemporaneous preparation be labelled as the BP mixture?
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An assay is an investigative (analytic) procedure for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity of a target entity (the analyte).
E.g percentage purity of a given substance, viscosity, bulk density, total organic content etc.
The analyte can be a drug, a biochemical substance, or a cell in an organism or organic sample.
Extemporaneous preparation refers to the preparation (mixing, assembling, packaging and labelling) of a medicinal product by a pharmacist (or licensed practitioner) according to prescription requirements for a specific patient . Extemporaneous preparations are made in relatively small quantities for short-term supply and use.
For example: Magesium trisilicate mixture can be extemporaneously prepared from the following:
(Magnesium trisilicate mixture is an oral suspension containing 5% w/v of these excepients in suitable vehicle.)
Guidelines of extemporaneous preparations can be found in the Pharmacopoeia.
Where you want to determine the content of say one of the excepients , is assaying. For example you may wish to experimentally find the actual content of magnesium in the mixture, you may perform titration with a suitable standard solution, then you can actually be able to calculate its percentage weight in volume