Calculating the Correct Amount of Desiccant for Pharmaceuticals
Desiccants protect your pharmaceuticals by reducing air humidity. Thus, a barrier layer is needed to limit the air exchange. Desiccants come in various forms and have found its important place in the packaging of various pharmaceuticals.
Before selecting the type of desiccant, calculating the correct amount of desiccant is important for maintaining the efficacy of the product and it depends on the following parameters:
- Identifying the type of container. It differs for flexible (eg: foil or polybag) and rigid type (eg: drum or pail)
- Calculating the surface area of the container walls in ft 2 or in 2 for flexible; or the volume of the container in gal., ft3 or in3 for rigid.
- Adsorption rate and adsorption capacity of the desiccants being used.
- A number of units required also differs for flexible containers and rigid containers.
Types of Pharmaceutical Desiccants:
It contains silica gel made from amorphous sodium silicate that is highly absorptive in nature or composition. It absorbs 40% of its own weight and is highly absorbing material unlike others in the market. It is hard, translucent material with an extremely high capacity for moisture at temperatures below 75? F and humidity levels above 40 percent. It is characterized by stable properties, non-toxicity, excellent moisture absorption performance and does not affect any products it comes in contact with. It is especially suitable for the moisture-proof packaging in the pharmaceuticals.
Activated carbon used in controlling objectionable odors and gases through the process of adsorption. Activated carbon has been used extensively for many years as an adsorbent of odors and toxic gasses and it performs unmatchable functions when it comes to adsorption of odours.
Molecular sieve is a very aggressive desiccant that can be used to quickly absorb moisture and odor. Molecular sieves are alumino silicates, a crystalline porous solid with a three-dimensional network with different pore sizes (3-5 Å). They have to be activated prior use and also can be regenerated at higher temperatures (180 oC - 260 oC) .It comes in the form of beads which has specific pore sizes.
Montmorillonite clay is a naturally occurring adsorbent created by the controlled drying of magnesium aluminum silicate. It is a free-flowing granular material with high moisture adsorbing ability from 20 to 80 percent relative humidity under normal packaging and storage conditions.
An important factor that adds to the efficiency of any desiccant is the cover stock, which means material used for its packaging. The cover stock must allow the desiccant to perform its functions without causing any harm to the product. The cover stock allows the desiccant to maintain an acceptable adsorption rate. One common cover stock used widely is Tyvek, a spunbonded, high-density, polyethylene.
Hence, one should always be mindful of all the characteristics of the desiccants and material used in its packaging as well as the packaging of pharmaceuticals. All these parameters are specific to the desiccants in question and therefore are important for the consideration in order to obtain the desired results.