Pharmaceutical Companies package their drugs according to standards stipulated by the government. These stipulations also specify the inclusion of a pharmaceutical desiccant in the packaging. Desiccants are vital to any form of packaging as they are hygroscopic substances; they make water molecules in the surrounding stick onto their surface.
Desiccants are porous substances that trap the water molecules within their molecular structure. Pharmaceutical drugs require this as moisture can completely disintegrate the drug, either reducing its potency or making it unfit for consumption.
Moisture also encourages fungus growth; this is not only highly unhygienic, but it can also alter the chemical composition of certain tablets. A desiccant prevents this from happening by sucking out all the moisture inside the packaging of the drug. Drugs stored under these conditions have a longer shelf life.
Types of Desiccants
Any substance with sorbent properties is a desiccant used in packaging. Most desiccants are chemically inert; they don’t cause a chemical reaction on contact with a drug. But certain desiccants can cause a chemical reaction if in contact with other chemicals and thus must be handled with care.
Any hygroscopic substance that can suck out moisture and is recognized by the regulatory Government body is fit for the packaging of medicines and pharmaceutical drugs.
Desiccant classification as Type I, II, III, IV, or V depends on their moisture sorption isotherm. Silicon, activated carbon and zeolites are some well-known desiccant examples.
Silica Gel
A silica gel desiccant is probably the most commonly used type of desiccant, not only in pharma products but also in the packaging of regular consumer products. Silica gel is the granular form of silicon dioxide, synthetically produced from sodium silicate.
Silica gel is inert, vitreous (glass-like shine), and porous. Silica gel works through the process of adsorption. When air moves through the silica gel, the water molecules in it get trapped inside the gel, and as the air passes out, it is moisture-free.
If silica gel reaches temperatures of 180°F or 82°C, it expels the water that is trapped within. In any case, storing drugs at that temperature is not advisable, so this regeneration process does not occur.
Activated Carbon
Activated carbon is a potent desiccant that eliminates moisture and odor; this has made it a very popular desiccant in many industries as well as for pharma uses. Activated carbon can also store gas within its molecular structure along with water.
They have a vast surface area in comparison to other desiccants. Their surface area to weight ratio is 3000m2 per gram. This large surface area allows for it to be extremely porous, allowing it to trap more water and odor-causing molecules.
This desiccant has adsorbent capabilities at even high temperatures up to 1470°F or 800°C. At this temperature, the carbon is burnt and releases the water it holds.
Even then its threshold is much higher in comparison to other desiccants. Its gas absorbing properties have made it a statutory addition to gas masks. Research into its other uses is still underway.
Zeolite or Molecular Sieve
Molecular sieves or Zeolite is the most popular desiccant used in pharma product packaging, and many claims suggest that it is the best desiccant for pharmaceutical drugs.
Molecular sieves have uniform pores that only allow tiny molecules to pass through; this allows for the air to pass through while the water molecules, which are bigger than that of air, get trapped in the sieve.
The most common material used to make molecular sieves is Zeolite. Zeolite is a naturally occurring aluminosilicate and is microporous. This desiccant can remove moisture content effectively to lesser than 100PPMv (Parts Per Million of Volume) to relative humidity.
Like other desiccants, this too can regenerate the trapped moisture when heated at 1022°F or 550°C; This makes it resistant to all humid climates, and as it has a large surface area, it can also absorb more water than silica gel desiccants.
Custom Blends
A pharmaceutical desiccant can also be a blend of different types of desiccants. These desiccants are packed in a porous packet and sealed. This packet is then placed along with the drugs while packaging.
Even standalone desiccants, i.e. non-blended desiccants, are packed in the same manner. Custom blend desiccants allow for more efficient absorption of moisture content, as it blends the features of two or more desiccants in one package.
For example, activated carbon has an additional characteristic of odor control. Combining this with a molecular sieve (Zeolite) which has higher adsorption can maintain aridity for more extended periods.
