The base material is always considered to be the bulk element
of a compressed tablet. This is usually made up of powdered sweetener which is
either compressed into a tablet or held together by using a binder. As this
report focuses on effervescent tablets, the chance of using a binder is less
because a binder has the possibility to prevent rapid dissolution of the tablet
when immersed in water. But depending on the nature of the sweetener used, the
tablet formulation might rarely include a binder that not only holds the
particles together prior to compression but also dissolve rapidly in water. Usually
the tablet also consists of an ingredient called the disintegrant which may be
used to help in breaking down the tablet during consumption. As this report
focuses exclusively on the effervescent aspects of formulation, it ranks excipients
like the disintegrant lower. Acids, flavours, high intensity sweeteners and colours
are the main excipients illustrated in the report. Last but not the least,
other functional ingredients such as the active ingredients, like vitamins or as
in this case acetaminophen are also added. The following sub-headings explain
the effervescent excipients in detail.
are substances that are used to induce acidity in effervescent reaction. There
are three main ingredients used to achieve this: organic acids, acid salts and
acid anhydrides. Traditionally, the usual sources of acidulants are organic
acids such as citric and tartaric acid but nowadays even acid salts are being
used for this purpose.
acid is the most commonly used food acid due to its abundance and relatively
cheaper pricing. It is high acid strength, highly soluble and also free-flowing.
It can be obtained as a monohydrate as well as an anhydrate. There are several
varieties in particle size grading such as colourless, white or translucent
crystals and also from granular to crystalline powder. The prime reason for its
usage is to modify the pH of the effervescent solution. It acts as an efficient
neutralizer. It is also used as a flavour enhancer and induces a freshness
effect into the product.
monohydrate has a melting point of 100 °C and losses water at 75 °C and at 135
°C it becomes anhydrous. Citric monohydrate effloresces at relative humidity
less than 65 % and at 25 °C. It turns into anhydrous below 40% relative
humidity. Approximately between 65 – 75% this acid absorbs inconsequential
amounts of moisture. It is considered to very hygroscopic, thus care must be
taken in packaging and storage to prevent exposure to humidity in high humid
It is a
soluble organic acid which absorbs moisture insignificantly at relative
humidity approximately up to 65%. It is more soluble than citric acid but is
also more hygroscopic. This acid is known for its high carbon dioxide releases
but its disintegration time is higher than its citric acid counterpart. Due to
this reason, this acid is allowed to form molecular compounds such as salts and
co-crystals with the active ingredient in order to improve its characteristics
of the rate of dissolution and solubility.
This acid is not hygroscopic, thus, the
crystals of this acid have a very good tendency of not absorbing moisture from
the atmosphere. This makes ascorbic acid as one of the very few pharmaceutical
ingredients that can be used to produce effervescent tablets in a
non-air-conditioned location. This acid crystal varies from white to yellow or
even colourless. These crystals are light sensitive and changes colour when
exposed to sunlight. The rate of dissolution, release of carbon dioxide and
solubility is comparable with that of citric and tartaric acids. The only
disadvantage of this substance is its relatively low tablet strength, thus this
ingredient requires a binder to hold the tablet in one piece.
It is a divalent acid whereas its
counterpart, the citric acid is a trivalent. This makes fumaric acid a more
efficient neutralizer than citric acid in terms of weight. It is also non-hygroscopic.
Despite of its advantages, fumaric acid possesses a solubility much lower than
citric acid and thus results in a slower reaction. Due to this reason fumaric acid is considered
to be a much more stable ingredient than citric acid.
acid ingredients include acetylsalicylic acid or also known as aspirin which
has a very low solubility characteristic.