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Medicated chewing gums are manufactured using any of the following methods
Most chewing gums are made using the conventional gum process. In this method, the gum base is melted or softened at about 60 oC after which it is placed in a kettle or Z-blade mixer to which active ingredient(s), and other excipients are added at a defined time to ensure a homogenous formulation. The gum is then sent to a series of rollers (kneading machine) that form it into a thin, wide ribbon.
During this process, a light coating of finely divided sugar or sugar substitute can be added to keep the gum away from sticking and to enhance any added flavour. The gum is then cooled for up to 48 hours in a carefully controlled room. This allows the gum to set properly. Finally, the gum is cut to the desired size and packaged as unit doses.
Note: Components of the gum base can also be added to the mixer in a solid form and are melted or softened through heating from the jacket of the kettle or Z-blade mixer.
This method has been developed with an attempt to lower the moisture content and alleviate the problems encountered in conventional method. Using a freezer apparatus, the gum base is cooled to a temperature (typically 15 °C or lower) at which the composition is sufficiently brittle and would remain brittle during the subsequent grinding step without adhesion to the grinding equipment.
The gum base can also be cooled using coolants like liquid nitrogen, hydrocarbon slush, or solid carbon dioxide. The refrigerated/cooled composition is then crushed or pulverized with a cutter or grinding apparatus to obtain minute particles of finely ground particles of the composition. The cooling and grinding steps can be combined by cooling the grinding apparatus.
After the grinding step, the coolant (if used) is allowed to evaporate and disappear from the chewing gum composition. The minute particles may be coated with edible substances or premixed with powdery materials in a suitable blender such as sigma mill or a high shear mixer.
For tabletization, compressing punches may be needed but an anti-adherent agent should be added to prevent sticking of finely ground particles/ granules on the punch faces.
This cost-effective method involves direct compression of tailored gum base powder or granulates mixed with active ingredient and other needed ingredients into a gum tablet using conventional tablet press. As the heating process involved in the conventional methods may constrain its use with thermally labile drugs, directly compressible, free-flowing powdered gums such as Pharmagum (SPI Pharma) and MedGuniBase (Gumbase Co) were proposed to simplify the process.
Pharmagum® is commercially available in three grades namely S, M and C. Pharmagum® M has 50% greater gum base compared to Pharmagum® S which primarily contains gum base and sorbitol. Pharmagum® M contains gum base, mannitol, and Isomalt.
MCGs formed by direct compression method are 10 times harder and crumble when pressure is applied resulting in faster release than MCGs formed by kettle fusion manufacturing method.
1. Increased amount of softeners and emulsifiers in gum base fasten release whereas hard gum may retard.
2. Cyclodextrin complexation or solubilization technique increases aqueous solubility of drugs that are poorly water-soluble.
3. Sustained drug delivery system can be achieved by binding a solid system of lipophilic active substance to cation exchange resin.
4. Release of active ingredients from MCGs can be modified or controlled using microencapsulation or agglomerations methods.
In addition to basic product quality tests (identification, assay, uniformity of content, and mass), additional tests specific to the product may be performed to ensure good quality. These may include, for example, texture analysis, product feel, and consistency, evaluation of flavors and sweeteners, tests for coatings, impurities, water content, etc.
As USP does not contain a compendial apparatus for evaluating performance of medicated chewing gums in many cases product performance data are generated by apparatus developed by drug product manufacturers and is not contained in the public monograph. However, when combined with basic product quality tests, performance test serves as a rugged and robust test to ensure the quality of finished products.
Read Also: Quality Control Tests for Tablets
Drug release test is one of the quality performance tests necessary for assessing medicated chewing gums. Due to the complexity of the release mechanisms involved in medicated chewing gum, researchers proposed minimal requirements for experimental settings with respect to the site of release and absorption.
The performance tests, however, must be able to detect the influence of critical manufacturing variables, discriminate between different degrees of product performance, and to some extent, describe the biopharmaceutical quality of finished products.
Besides the product quality tests, the drug release tests can provide useful information about the characteristics of the product itself, which includes but is not limited to the influence of the composition of the gum and other excipients on drug release, a main tool required primarily during product screening and development, and to some extent the product performance in vivo.
The European Pharmacopoeia (Ph. Eur.) has adopted an apparatus to determine the release rate from chewing gums formulations. The basic principle is a simple masticatory movement employed to simulate the chewing action on a piece of gum placed in a small chewing chamber containing a known volume of buffer solution are given temperature.
The drug release rate is influenced by the chewing rate and angle which provides the necessary shear force to expose new gum surfaces and is requisite for further drug release. For treatment of local oral conditions, a release period of less than 1 hour is desirable, but a faster rate may be required if a rapid onset is required for systemically absorbed formulation.
These include:
As a general rule, under sink conditions, the rate at which the drug is released is directly proportional to the chewing frequency and aqueous solubility of the drug substance and is indirectly proportional to the mass of the gum base.
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