Formulation, Manufacture and Evaluation of Chewable tablets

Production techniques in chewable tablet Formulation

The manufacture of chewable tablets basically follows the design/ pattern for conventional tablets. The wet granulation method is usually employed. However, other methods such as direct compression, and dry granulation or slugging/pre-compression may be employed depending on the nature of the excipients being used.

The formulation of chewable tablets is designed to include substances that impart or improve palatability and pleasant, cooling sensation. Palatability is usually provided by the addition of suitable flavouring agents. These are added to the other usual tablet excipient excepts disintegrant. Disintegrants are not usually included in chewable tablets since they are meant to be broken down by chewing.

Steps involved in the manufacture of chewable antacid tablets

Typical formula for a chewable antacid tablet formulation

To prepare Aluminum hydroxide and Magnesium hydroxide chewable tablets using the formula above follow the following steps:

1. Mix the first four ingredients in a suitable blender
2. Add items 5 and 6, us this to moisten the mix of the first four ingredients
3. Granulate by passing through a l4-mesh screen
4. Dry at 140 to 150 °F (60.00 to 65.56 °C)
5. Size through a 20-mesh screen
6. Add and thoroughly mix items 7, 8 and 9
7. Compress using 0.5-inch, flat-face, bevelled-edge punches.

Methods of improving flow properties of powders during manufacture of chewable tablets

In order to obtain a suitable solid chewable tablet formulation, two critical properties of the ingredients, namely, ability to flow well and compressibility are generally taken into consideration. Good flow properties of the material (ingredients mixture) are necessary for easy passage from the hopper of the tablet machine to, and adequate filling of, the dies.

To enhance powder (or granule) flow, the following may be done:

1. Addition of glidant (e.g., fumed silicon dioxide) to the formulation
2. Formation of spherical particle may be made to be spherical by either by spray drying or spheronization
3. Particle size enlargement by granulation
4. Mechanical agitation using vibrators. This is no longer recommended due to the problems of particle segregation and stratification.

Granulation is the most popular method of improving flow properties since most powdered ingredients can be granulated. In most cases, granulation also improves compressibility of powders, that is, the ability of the granules to form a stable, intact mass on application or pressure.

Taste masking/ Overcoming the bitter taste of some active ingredients

Taste masking is defined as a reduction of undesirable taste that would otherwise exist. It will be beneficial when the taste and palatability of a drug substance is likely to be unpleasant to patients or when the dosage form has a high degree of interaction with patients’ taste buds as is common with chewing and orally disintegrating tablets, gums and gummies.

Taste masking can be achieved using taste-masking agents, specific flavours and sweeteners. Sweeteners are essential to complete the experience and produce a pleasant taste of the product. Some techniques which have been used in taste masking include:

1. Coating by wet granulation
2. Microencapsulation (especially phase separation and coacervation)
3. Solid dispersions
4. Adsorbate formulation techniques (Solvent method)
5. Ion Exchange
6. Spray congealing and spray coating
7. Formation of different salts or derivatives
8. Use of amino acids and protein hydrolysates
9. Inclusion complexes
10. Molecular complexes

For effective taste-making, certain factors have to be taken into consideration. These include:

1. Level of masking required
2. Dose size
3. Physicochemical properties of the drugs
4. Influence of substrate properties (particle size and shape)
5. Selection of flavouring and sweetening agents
6. Formulation strategies

Quality control tests for chewable tablets

The following important quality control tests are carried out on chewable tablets

1. Content of active ingredient
2. Uniformity of content of active ingredients
3. Uniformity of weight test
4. Organoleptic properties
   1. Taste
   2. Mouth feel
   3. Colour
   4. Odour
5. Chewing property
6. Stability test
7. Friability test
8. Hardness test

Other tests carried out to ensure quality of the chewable tablets include uniformity of thickness, uniformity of diameter and measurement of tablet density.

Note: Disintegration time test is usually not required for chewable tablets

Examples of Chewable Tablets

• Claritin – Loratadine 5 mg (Bayer)
• Montair – Montelukast 4 mg and 5 mg (Ascent Pharma)
• Lamictal – Lamotrigine 5 mg, 25 mg, 50 mg, 100 mg, 200 mg (GlaxoSmithKline)
• Mylanta Gas Minis- Simethicone (McNeil Consumer Pharmaceuticals Company)
• Danacid – Compound magnesium trisilicate tablet (Dana Pharmaceutical Ltd)
• Lipitor – Atovastatin 10 mg (Pfizer)
• Natecal D3 – Calcium 600 mg + Cholecalciferol 400 I.U. (Chiesi Limited)
• Imodium Advanced – Loperamide Hydrochloride 2 mg + Simethicone 125 mg (McNeil Consumer Pharmaceuticals Company)
• Alzol – Albendazole USP 400 mg (Rene Industries Ltd)
• Tylenol – Acetaminophen 160 mg (McNeil Consumer Pharmaceuticals Company)
• Epanutin Infatabs – Phenytoin 50 mg (Pfizer)

Advantages of Chewable Tablets

• Patient convenience; can be taken at any required time and place when water is not available.
• Increased bioavailability resulting from increased absorption rate, due to its dissolution or being chewed in the mouth into the gastrointestinal tract (GIT) in solution or granule form.
• Improved patient acceptance (especially pediatric) through pleasant taste
• Possible to use as a substitute for liquid dosage forms where immediate pharmacological action is desired.
• The large size of the dosage form is difficult to swallow. In such cases, chewable tablet offers advantages over it
• Effectiveness of therapeutic agent is improved by the reduction in size that occurs during mastication of tablets before swallowing

Disadvantages of Chewable Tablets

• Bitter or foul-tasting drugs are not good candidates for chewable tablet formulation.
• Chewable tablets contain sorbitol which causes diarrhoea and flatulence
• The presence use of flavouring agents in chewable tablet may cause ulcer in the oral cavity
• Prolonged chewing of chewable tablet results in pain in facial muscles
• Chewable tablets are hygroscopic in nature, so must be kept in a dry place
• They show the fragile, effervescence granules property
• Since these tablets have insufficient mechanical strength, so careful handling is required

References

• British Pharmacopoeia (2009).
• Lieberman, H., Lachman, L. and Schwartz, J. (1989). Pharmaceutical Dosage Forms: Tablets Vol 1. New York: Marcel Dekker, Inc.
• Mbah, C. (2015). Lecture on Personal Collection of Mbah, University of Nigeria, Nsukka, Enugu State.
• Niazi, S. K. (2009). Handbook of Pharmaceutical Manufacturing Formulations: Compressed Solid Products. New York: Informa Healthcare USA, Inc.
• Ofoefule, S. I. (2002). Textbook of Pharmaceutical Technology and Industrial Pharmacy. Nigeria: Samakin (Nig) Enterprise.
• Rowe, R., Sheskey, P. and Quinn, M. (2009). Handbook of Pharmaceutical Excipients. USA: Pharmaceutical Press and American Pharmacists Association.
• United States Pharmacopoeia (2007). The US Pharmacopoeial Convention. 35th edn. Inc.12601 Twinbrook Parkway, Rockville MD20852.
• WHO Drug Information Vol. 25, No. 3, 2011. available online at: http://www.who.int/druginformation.

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