Sources of carbon dioxide:

Sodium bicarbonate:

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              There are
two main sources of carbon dioxide namely, carbonates and bicarbonates. But
bicarbonates are the ones that are used often. Sodium bicarbonates (NaHCO3)
is a white, odourless, crystalline powder with a slightly alkaline and a saline
taste. It’s efficiency of carbon dioxide yield is 52%. It’s stable below
relative humidity of about 80% and approximately above 85% it starts to
decompose. This compound has the tendency to undergo decarboxylation in humid
air.

Sodium carbonate:

              It is yet
another source of carbon dioxide but is an anhydride, available either in monohydrate
or a decahydrate. This compound is hygroscopic in nature.

Potassium bicarbonate:

              Potassium
bicarbonate is a highly water soluble compound. This compound requires a
temperature of about 200 °C to decompose and is higher than sodium bicarbonate.
This compound is also hygroscopic and requires an 80 % relative humidity to get
hydrolysed.

Other sources:

              Potassium
carbonate, calcium bicarbonate and other amino acid–alkali metal carbonate
derivatives, such as sodium glycine carbonate.

Sweeteners and flavours:

              These
excipients are used to produce tablets that are palatable to the taste senses
of the patient. There are generally two types of sweeteners: natural and
artificial. Due to the constant raise in popularity for natural based
ingredients, the natural sweeteners are used more often. The natural sweeteners
are carbohydrates that primarily consists of carbon, hydrogen and oxygen
molecules.  The types of sugar in a
hierarchical order is explained as follows,

Monosaccharides:
The simplest form of sugar is called monosaccharide, which is made up of
glucose, fructose and galactose.

Disaccharides:

The combination of two monosaccharides produces
disaccharides. The following combination of monosaccharides produces the
respective disaccharides: glucose + glucose= maltose, glucose + fructose=
sucrose, glucose + galactose= lactose.

Tri and polysaccharides:

A trisaccharide consists of three monosaccharides, whereas
tetrasaccharides consists of four monosaccharides. These sugars are
indigestible and thus are not used as sweeteners. When there are greater number
of monosaccharides attached to a single chain then they are called as
polysaccharides. There are two types of  
polysaccharides, the ones that are digestible and the one that are not
digestible Starch is a long chain of glucose units from which corn sweeteners
are obtained. Whereas on the other hand, lignin, cellulose and gums are
non-digestible polysaccharides.

 

Sweeteners are also classified based on its nutritional
value as nutritive and non-nutritive. Nutritive sweeteners include sucrose,
honey, stevia, polyols, etcetera, whereas non-nutritive ones are the artificial
ones namely aspartame, saccharine, neotame, etcetera.  

Polyhydric alcohols:

Sorbitol, glycerine, mannitol, propylene glycol, and xylitol
are examples of polyhydric alcohols or polyols. They are produced by the
process of hydrogenating the corresponding reducing sugars, for example,
sorbitol is obtained by the hydrogenation of glucose. They are mainly used to
provide the texture and bulkiness of sucrose but contain lesser kilocalories/gram.

Nutritive sweetener:

Sucrose is considered as a nutritive and is also the most
widely used sweetener. This report aims to compare the usage of other nutritive
sweeteners such as honey and stevia based on economic considerations.

Pre-formulation studies:

Pre-formulation data is
considered to be the first and foremost crucial step in any design or
formulation of a tablet. It is vital for every formulator to possess each and
every physicochemical profile of all active ingredient available, prior to
initiating the development of any formulation activity. The process of
compiling such information is known as the studies of pre-formulation. A
general pre-formulation data of active ingredients is shown below and this
responsibility usually lies on the pharmaceutical chemistry research team.

1. Solid state stability: light, humidity, temperature.

2.Solution stability: drug-excipient stability. The differential
thermal analysis or other accelerated methods are used to determine this factor
of the drug.

3.Solid mechanical properties: bulk density, particle size
and tap density, melting point, colour, taste, odour, appearance, compressibility,
crystalline form, etcetera.

 4.Physicochemical
properties: Solubility, pH profile of the dispersion, etcetera.

5. In vitro dissolution: absorbability of pure drug, pure
drug pellets, effect of excipients and surfactants, dialysis of pure drug.