Stability Of Drugs:Packaging And Stability
From Pharmpedia
Packaging of the drug product is very important when its stability is being considered. The immediate container and closure are particularly important in affecting product stability. Glass, plastic, rubber (natural and synthetic) and metal are the four types of containers commonly utilized for packing drug products.
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Glass
Glass is resistant to chemical and physical change and is the most commonly used material, but it has the limitations of :
1. Its alkaline surface may raise the pH of the product.
2. Ionic radicals present in the drug may precipitate insoluble crystals from the glass
3. The clarity of the glass permits the transmission of high energy wavelength of light
which may accelerate decomposition.
All these limitations are overcome by the technologists in the following way: (1) the first problem is overcome by the use of Borosilicate glass which contains fewer reactive alkali ions, (2) Treatment of glass with chemicals or the use of buffers helps in overcoming the second problem, (3) Amber coloured glass which transmits light only at wavelengths above 470 nm is used for photolytic drug products.
Plastics
Plastics include a wide range of polymers of varying density and molecular weight, each possessing different physicochemical characteristics. The problems with plastic are:
1.Migration of the drug through the plastic into the environment.
2.Transfer of environmental moisture, oxygen, and other elements into the pharmaceutical product.
3.Leaching of container ingredients into the drug.
4.Adorption or absorption of the active drug or excipients by the plastic.
For all these problems the solution is to suitably pretreat the plastic chemically. The drug product packed in the final container must be tested for stability.
Metals
Various alloys and aluminium tubes may be utilized as containers for emulsions, ointments, creams and pastes. They may cause corrosion and precipitation in the drug product. Coating the tubes with polymers or epoxy may reduce these tendencies.
Rubber
Rubber also has the problems of extraction of drug ingredients and leaching of container ingredients described for plastics. The use of neoprene, butyl or natural rubber, in combination with certain epoxy, Teflon or varnish coatings reduces drug-container interactions. The pretreatment of rubber vial stoppers and closures with water and steam removes surface blooms and also reduces potential leaching.
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