In a Glass of its Own

In today’s pharma industry, glass breakage is mainly related to older filling lines, but the increasing number of highly toxic and/or sensitive drugs is driving innovation in glass technology. The key is to work with a supplier to meet your specific needs – and keep down the regulatory hassle.

By Professor Volker Rupertus, Senior Principal Expert for SCHOTT, and Dr. Folker Steden, Director Product Management and Scientific Services, SCHOTT Tubing.

Some may find this surprising, but if you stand on top of a beer bottle and load two or three of your friends onto your shoulders, the only thing you’ll risk breaking is your neck. Glass possesses remarkably high strength, and in the pharma industry, breakage out in the “field” – either during logistics or even in pharmacies and hospitals – rarely happens. In fact, a competitor recently told us that they had once spent hours repeatedly dropping glass syringes from an office table in the hope of filming a breakage – with no luck. Hospitals usually have synthetic flooring that helps prevent vial breakage, but the main reason is simply that glass is very resilient.

Glass will only break if the mechanical load applied to the item, multiplied by the “criticality” – pre-damages, such as scratches – is greater than the strength of the glass. This means that a perfectly shaped piece of glass can survive tremendous mechanical loads, but with pre-damage, the risk of breakage is much greater. Glass breakage in the pharma industry tends to occur during processing, and is often related to the age of the filling equipment. Companies with state-of-the-art technology tend to experience very few breaks, whereas companies that run their products on old filling equipment and filling lines will experience more.

Glass has a memory

They key to reducing glass breakage resulting from old filling technology is to reduce the amount of pre-damage. A common phrase in the glass industry is that “glass has a long memory,” which means predamage, either to the glass tube or the final container, cannot be undone – the damage will be carried through the whole process. By preventing pre-damage, you can easily secure the breakage resistance of a glass container at its highest value by nature.

With Schott’s perfeXion™ initiative, the entire surface of every single tube is checked for pre-damages. Later on during the converting step, further improvements can be achieved with advanced forming technologies combined with inspection technology – this also helps to avoid scratches and reduce particle load in the container significantly. In short, packaging with a high cosmetic quality secures the breakage resistance of the container beyond what is required for most of the industry.

There are certain market niches, however, where the chance of breakage must be reduced beyond what would normally be required. The problem of old filling machines will fade over time as the packaging industry continues to work on improved glass handling, advanced transport and logistic concepts and RTU solutions. Yet radioactive contrast media or certain oncology drugs, for example, can be very toxic, and companies must ensure that breakage never occurs. Another example is drugs intended for use in warzones, where the containers must be highly break resistant (for obvious reasons). The question remains if these applications can be addressed with existing solutions, or if pharma companies have to switch to new solutions and go through all the regulatory headache associated with this.

Is there a perfect type of glass?

Type-I borosilicate glass has been the gold standard for pharmaceutical packaging for over a century. As a result, there are thousands of data sets and long-term trends for all kinds of formulations available. This helps to reduce risks in the selection process for new containers. Containers are now coming onto the market that use a different glass composition – aluminosilicate glass – more commonly found in mobile phone covers and halogen lights. Schott is in a good position to comment on both glass types, as they have been part of our portfolio for decades. We have been supplying aluminosilicate glass to consumer electronics industries worldwide, and this glass is also the basis for glassceramic applications such as CERAN^® cooktops.

Aluminosilicate is certainly an interesting glass type, but the feedback we get from our customers is that there is reluctance to perform the studies to characterize drug-container interaction, the extractable and leachable profile over the lifetime of a drug product, and so on. There’s no scientific track record in terms of interaction between drug components and the glass surface, and, understandably, companies that don’t have any problems aren’t keen to take on additional validation.

It’s also important to differentiate glass properties from container characteristics – achieved during post-processing. What drives the break resistance is not the glass composition, but rather the posttreatment process. Borosilicate glass is a very neutral material, which – without further treatments – shows the lowest reaction between chemical products and glass itself. Aluminosilicate glass, in turn, needs intense treatment (e.g. ion exchange in the glass surface and therefore an undefined gradient in the near-surface glass composition) to reach the same level.

The good news is that literally any desired property, such as reduced risk of delamination or breakage resistance can be achieved with borosilicate glass that has already been approved by regulatory bodies. For example, it can be chemically strengthened through an industry standard ion exchange process to produce tougher metrics: a five to ten-fold higher break resistance. For an industry that wants to reach a cost/benefit optimum this is the better way to go.