Detecting Integrity Breaches In A Range Of Pharmaceutical Blister Package Types

By Dr. D. Dixon, University of Ulster

Demonstrating the integrity of pharmaceutical blister packs is critically important, as any defects can affect the shelf life and efficacy of the contents. Compared to bulk packaging, blister packs offer improved product integrity, tamper evidence and reduce the likelihood of misuse1, 2. Packs can be composed of either a thermoformed polymer or cold formed aluminium tray, with a number of individual pockets to hold the product. After the tablets or capsules are placed in the pockets, the packs are heat sealed with a paper or foil laminate sheet. These various stages can be completed separately or integrated into a single form, fill and seal process. There is a risk of microbial containment or degradation of the contents if any defects are present in the packaging. Such defects can take the form of rips or pinholes in the tray, or lid materials, faulty seals and channel leaks between pockets.

Methylene blue dye testing is commonly used for the routine testing of blister packs. Packs are immersed in water which has been dyed blue and subjected to a vacuum of typically 400- 600mBar for several minutes. The vacuum will draw air from faulty packs leading to the ingress of dye when the vacuum is released. Inspection for the presence of dyed water inside the blister packs is undertaken manually3. While the technique is widely accepted industrially, the detection of small defects is reliant on human subjectivity and operator vigilance. Blue dye testing is also destructive with the requirement to destroy all tested packs.