Chewing Gum as a Nutraceutical Delivery System

by Nebiyou Getahoun, Ph.D.

Gum bases have been used since around 50 A.D. The ancient Greeks were believed to chew mastiche, a product from mastic trees, and the Mayan Indians were also known to use chewing gum from the spodilla tree. Chewing gum was first introduced to the public around 1848. During World War II, the shortage of natural gum created the need to develop synthetic gum bases.

The intended benefit of gum was originally for pleasure and to freshen the breath. This important matrix was later discovered as a drug delivery to the uccal and sublingual cavity. Medicated gum, such as Nicorette nicotine chewing gum, was introduced to the market around 1978. As a delivery technology, gums offer water-free administration, fast onset of action and low systemic side effects.

Formulating with gum involves understanding the rheology, as well as the effects of various ingredients. Gum base, when stretched or subjected to deforming forces, exhibits both flow and elastic behavior. For instance, if stretched and held for some time then released the gum will elastically contract, but to a length that is longer than its original length. The viscoelastic properties of gum base can change, depending on the kind of excipients, amounts, processing conditions and the mechanical history. The thermodynamic and molecular interactions of excipients with the gum base can be major factors accounting for these changes.

Synthetic gum bases can contain a variety of ingredients, including insoluble wax, elastomers, softeners and fillers. Gum products designed to deliver active pharma or nutritional components generally include other items, including humectants, antioxidants, buffers, sweeteners and flavors.

In fact, the presence of flavors is essential. It is possible to use either water insoluble and/or water-soluble flavors. The amount of flavor released depends on the partitioning of the flavor between the gum and saliva. Thermodynamically speaking, the driving force of flavor can be different in chemical potential between the gum phase and saliva phase. It also depends on the diffusion process of the flavor, which is influenced by the tortuosity and porosity of the gum base. This also holds true for the release of drug particles from the gum base.

The chewing process also alters the texture of the gum. The gum firmness changes with chewing time. The gum is initially firm during storage to maintain its shape. During the first two to three minutes of chewing, the gum is softened and hydrated by the saliva. After the sweeteners and flavoring agents are chewed away after about three minutes, the gum will become firmer again. In most cases, the firmness gradually stabilizes at about six to eight minutes. As a general rule, the pieces of elastomer make the gum firm, while plasticizers make the gum texture soft.

In addition to the flavor, the presence of other ingredients, such as humectants and buffers, can change the chewing properties of the gum base. Since the major function of the chewing properties dictates the release of a drug, understanding the fundamental rheological properties of gum base can help predicate the gums properties during formulation, manufacture and chewing.

By definition, rheology is the study of the deformation of matter due to an applied force. The type of deformation property varies depending on the matter that undergoes deformation process. One of the properties that rheology deals with is viscoelacticity.

When gum base is used as a drug delivery system, buffers play a major role in forming a pharmacologically acceptable environment (acceptable pH). Therefore, the role of pH in the gum delivery system is also important.

In the past, chew-out studies were done to understand the release of drug substance from gum matrix. These studies involve human subjects chewing a gum for a specific period of time; the gum is then analyzed for the remaining amount of active. This method at times can be challenging since standardization is difficult due variable factors associated in chewing process.

Mastication machines can provide in vitro release profiles for actives in gum-base products. When using a mastication machine, some factors that affect the active release profile from the gum base are temperature of the test medium, the chew frequency, the chew time and the torsion angle.

In conclusion, a chewing-gum base can be an alternative and effective nutraceutical delivery system provided the formulator and producer understand the rheological phenomena, release profile and the interaction of gum base with the other ingredients.

Nebiyou Getahoun, Ph.D., is the president of Bethlehem, PA-based Pharma-Med Inc. Learn more at Pharma-Medicine.com .