According to the market research firm Freedonia Group, plastic bottles with standard closures continued to retain a sizable portion of pharmaceutical packaging--about 32%. Generating one of the fastest growth opportunities, however, are blister packs.

Also known as unit dose packages, blisters make up about 23% of pharmaceutical packaging currently available. In fact, the demand for unit dose formats surpassed that for bottles in 2001 with $775 million for blister packaging as opposed to $755 million for bottles. By 2006, the demand for blister packaging used for pharmaceuticals will reach $1 billion, while that for bottles will be about $905 million.

In addition to assessing new shapes and configurations to enhance brand identity and consumer safety, the challenge is selecting the right type of film for the blisters in terms of property, grade, thickness and barrier.

A blistering range of materials

A variety of materials can be used to form the blister cavity, including the more commonly used monolayer polyvinyl chloride (PVC) or two-layer coated polyvinylidene chloride (PVDC). Even though pharmaceutical companies may be reluctant to switch materials they currently use for blister packaging due to cost and production time for development, the interest in alternative materials continues to grow.

Going beyond PVC or PVDC, other material considerations for blister packaging include: PVC/PVDC coated films; chlorotrifluoroethylene (CFTE); and cycloolefin copolymers (COC).

1. PVC/PVDC coated films

Polyester applications could be a conceivable alternate but, since it has relatively high water vapor permeability compared to PVC, its chance for universal adoption is slim. But an option could be PVDC coated polyester resulting in similar water vapor barrier as PVC. However, coating polyester with PVC defeats the goal of replacing chlorous plastics particularly where environmental considerations are concerned.

Because there is a worldwide demand for generic drug products, Perlen Converting AG--a Swiss based manufacturer of pharmaceutical films--has developed a pharmaceutical grade film that offers a more economic alternative to existing PVDC coated films. Called Perlalux-Generex, it provides barrier properties on par with standard duplex films and higher than mono PVC. Perlalux also requires less heating/energy used during thermoforming.

2.Chlorotrifluoroethy lene

Other alternative blister materials include variations on chlorotri fluoroethytene (CTFE) homopolymer-based barrier films. This material thermoforms easily, displays high moisture barrier and, if desired, can be laminated with a range of materials including PVC, polypropylene (PP) and polyester.

Another key benefit includes crystal clarity of the film permitting easy product and dose identification. The film can also be thermoformed into tinted blister cavities and has barrier properties close to foil. The chemically inert film will not alter the taste of flavored products and complies with FDA regulations.

There are mid-range CTFE films available that won't degrade rapidly under elevated heat and humidity conditions and have barrier performance that increases after thermoforming. CTFE specifically addresses the substantial growth opportunities for pharmaceutical blister packaging in European, South American and Asian markets. These particular films (for instance, Honeywell's Aclar films) are comparable to various grades of PVDC but will not yellow or grow brittle over time.

3. Cycloolefin copolymers

Cycloolefin copolymers (COC) provide long term protection from moisture with some grades providing nearly 10 times the moisture barrier of PVC. COC has high clarity and stiffness and is compatible with standard thermoforming tooling and traditional blister backings or liddings. It also has a low density, so it yields more film per pound of resin.

COC is typically used as the core layer in blister formations, in both coextruded and three-layer laminated film structures. Outer layers consist of PP, but other polymers such as PVC, or polyethylene (PE) can be used.

COC has a wide processing window and cart be used on standard blister lines with little adjustment.

-- Stagnito Communications