The new products, sold under the Tekniflex brand name, are the first to combine Topas cyclic olefin copolymer (COC), supplied by Germany's Ticona, and polychlorotrifluoroethylene (PCTFE).
PVC is still widely used in blister packs, but is criticised because its combustion results in hydrochloride emissions, and if combustion takes place under certain conditions it can produce dioxins. For this reason some manufacturers have been moving away from the use of PVC, especially in Scandinavia where legislation is now in place discouraging its use as a packaging material, said a spokesperson for the company.
However, others take the view that pharmaceutical use of PVC is so small (2 per cent) in comparison to the building industry that replacing PVC is irrelevant from an environmental perspective.
Traditional blister films combine a relatively thick layer of PVC or polyethylene terephthalate (PET) that has excellent thermoforming properties with a relatively thin layer of a barrier polymer like PCTFE or polyvinylidene chloride (PVDC). In a COC/PCTFE structure, the COC layer is both the thermoformable carrier and a moisture barrier.
"The combined barrier of the Topas COC and PCTFE layers allows water vapor transmission to be reduced to levels that meet or exceed the best performing barrier films available," said Ticona in a statement.
In addition, pairing Topas COC and PCTFE allows overall thickness of the film to be reduced with no loss in moisture barrier.
Tekniflex COC-PCTFE grades are available with PCTFE thicknesses of 10 to 100 microns and COC thicknesses of 200, 250, 300 and 350 microns.
"The use of Topas COC and PCTFE in tandem makes an effective structure that thermoforms well on standard equipment," said Michiel van den Berg, director of global pharmaceutical packaging development.
He said that in one test series on formed blisters (at 40°C and 75 per cent relative humidity), Tekni-Plex found that a film using polypropylene as a forming layer with 300 micron COC and 23 micron PCTFE film had a water vapor transmission rate of 0.098 mg/cavity/day. By comparison, the transmission rate for a 250 micron PVC/23 micron PCTFE film was double this at 0.200 mg/cavity/day.
The choice of forming and sealing materials used depends on the degree to which the product needs to be protected from light, heat and moisture.
Each material has different resistance to each of these elements and will affect the shelf life and storage conditions of the packaged drugs. Stability tests are usually carried out during a drug's development to identify the most suitable materials.