Eye on excipients
In this edition of the column, Javier Belmar and Marc Ribé of Cafosa discuss the formulation and manufacture of direct-compression medicated chewing gum. Until recently, chewing gum required high-temperature extrusion. Today, formulators can use a combination of powdered excipients to create chewing gums that run on standard tablet presses.
Medicated chewing gum (MCG) is an oral dosage form that releases an API or functional ingredient by the mechanical action of chewing. It has gained interest as an alternative and highly attractive delivery system for several categories of products, including prescription and over-the-counter pharmaceuticals and dietary-supplement products. Until recently, MCG remained a niche pharmaceutical category best known for helping people quit smoking (nicotine replacement) and for treating motion sickness. Greater application of the dosage format was limited, however, due to its complex formulation and manufacture. The traditional process used in the confectionery industry requires hot mixing and extrusion that require technology and equipment unfamiliar to most pharmaceutical companies. The heat of the process alone made it unsuitable for many APIs.
Today, however, directly compressible excipients enable wider use of MCG production in pharmaceutical applications, and you can transform a mixture of dry powdered excipients and the API into a quality chewing gum product using a standard tablet press.
The excipients open up the dosage format to pharmaceutical and dietary-supplement companies seeking a new delivery system that is more convenient and attractive than other dosage formats, such as standard chewables, orally disintegrating tablets, sachets and lozenges.
Many consumers prefer a chewing-gum format: It adds a pleasant sensation to medicinal or functional products. It also provides mild stress/anxiety relief, increases alertness and concentration, reduces food craving by its satiety sensation, and boosts oral health by promoting saliva flow and increasing pH that fights plaque acids.
MCG does not require water and there is no tablet to swallow. The simple action of chewing releases the API and allows fast absorption through the oral mucosa, implying quick onset of action. In addition, MCG prolongs the API's residence time in the buccal area, extending the local effect.
Direct compression versus traditional extrusion
Using powdered excipients to directly compress chewing gum underscores its appeal to pharmaceutical manufacturers, many of whom see it as an innovative oral dosage format. The ability to continue using familiar processes and machinery is another benefit.
The standard (confectionery) process for making chewing gum begins with a heavy-duty, double-sigma mixer operating at about 50° C (Figure 1). Next, the mass is extruded, shaped, and packaged. It usually takes more than a day to obtain the finished product because the extrudates must cool before they can be coated and packaged.
Directly compressing chewing gum -possible because of the powdered excipients- has several advantages over traditional extrusion manufacturing:
- Identical to traditional tablet manufacture
- Dry mixing of powders
- Absence of heat
- Content uniformity of APIs
- Low water activity
Direct-compression chewing gum also has very good stability because the moisture content of the powder is very low, much lower than that of extruded chewing gum. Thus, APIs that are sensitive to heat or humidity are good candidates for use in chewing gum formulations.