In order to understand what desiccants and sorbents are and what they do, you first have to understand the difference between absorption and adsorption.
Absorption relates to one substance passing into the bulk of another medium, such as a sponge soaking up water. The medium that is absorbing and the substance being absorbed become indistinguishable. Drinking water is also an absorption process, the water becomes a part of you, indistinguishable from you and not discernible as water. In order to free the absorbed substance, energy has to be introduced, through movement or heat. Adsorption is a different process, it relates to one substance sticking to the surface of another. The adsorption medium and the substance being adsorbed remain separate, such that they are easily distinguishable and the attraction between the two is more easily broken. Imagine trying to soak up a coffee spill with a standard sheet of photocopy paper. The surface of the paper will attract some of the coffee through adsorption, but it will not be absorbed as would happen if you used a paper towel. One of the biggest adsorbent substances we know of is activated charcoal, which attracts a number of molecules to its surface and is used in many practical applications, such as gas masks, water filters, or environmental deodorants.
Substances that take in liquids and/or gases are generally termed sorbents, as they either ADsorb or ABsorb. Desiccants are a subset of sorbents that have a particular affinity for water and are commonly used to keep an environment drier than it naturally would be. Just about all materials attract moisture to some degree, but commercially used desiccants do it better. Desiccants, then, are the top solution for combatting environments with too much moisture. There are many desiccants on the market, and the choice of the appropriate one to be used within a product’s packaging is normally determined by the quantity of moisture it will need to sorb, the cost of the material, whether it can also be used to attract other substances, availability in a geographic area, etc.
We include desiccants with drugs to ensure moisture is taken out of the storage environment (in a pill bottle, for example) thereby reducing accelerated decomposition. A humid environment tends to break a substance down faster than a dry one. Also, humid environments tend to offer bacteria a medium where reproduction accelerates. These are the primary reasons behind why we find small desiccant packs in our medication bottles – to ensure the drug stays potent and to improve hygiene. Some materials will be used to adsorb gasses and moisture, other will absorb environmental moisture right away or over time.
Hence, one of the directions firms seem to be moving in is improving both by taking pills, capsules and such and moving them out of containers and getting them into blister packs to improve isolation from environmental contaminants. Firm Klöckner Pentaplast, for example, has released a new material called Pentapharm that’s making waves in the space, as it incorporates a desiccant into the material to offer excellent barrier properties that cut down moisture dramatically. CSP Technologies has done something similar with its Activ-Blister solution, ensuring even the most moisture and oxygen-sensitive solid drugs can be shipped in a blister format. Both seem designed to obviate the need for blister packs that offer a separate well area containing a desiccant connected to each blister, such as Tekni-Films’ Teknliflex range of blister packs.
By taking the desiccant out of the well and incorporating it into the film, valuable space is returned to the blister strips for actual product.
Other directions in the space are being championed by such firms as Impak, the company behind sorbentsystems.com, that offer a host of solutions for companies of all sorts. With such innovative concepts as desiccant papers and films, colour-changing cards that indicate humidity level, customizable molded desiccants, special caps and vials with incorporated sorbents, and many others, Impak offers firms a way to include desiccants in their drug packaging with the consumer never knowing it’s even there. By eliminating the need for exterior elements, in many cases the company’s products can cut down on costs related to having to bundle a sorbent pack or other solution with the merchandise.
The choice of the packaging is a key differentiator in the market. On the Webpackaging site, we recently saw a collaboration between Webpackaging member Pumpart Systems and Clariant Healthcare Packaging. Pumpart manufactures Tubairless®, the company’s smaller, lighter airless tube concept, and it was a natural fit to work with Clariant, a firm always looking to drive sorbent technology forward. In this case, the Tubairless system proved perfect for Clariant’s bid to offer companies with a liquid or cream product that had the same level of security as those the company offers to pill and capsule creators. Headquartered in Switzerland, Clariant recently invested in enhanced factory capacity as well as extended quality management to offer pharmaceutical firms desiccant solutions more rapidly and in larger volumes.
With new solid drugs being released yearly, each will need to consider what sort of environment it will require, and we may begin to see items on shelves that last far longer than anything previously thanks to innovative new sorbent materials.