A short guide to plastic pharmaceutical packaging

Plastic is an extremely versatile material, which is widely used for the production of packaging systems in various sectors, including the pharmaceutical industry, due to its characteristics of flexibility, mechanical strength and stability.

There are three main types of primary plastic packaging for pharmaceutical use:

• containers: bottles, pill bottles, dispensers, blisters, and ampoules;
• closures: caps of various kinds (screw-on, press-on, tamper-evident, child-resistant) or other kinds of closures, such as heat-shrink film;
• accessories: scoops, spoons, syringes, droppers, inhalers, and dosing accessories.

Types of plastics for pharmaceutical packaging

Of the numerous polymers available for the production of plastic packaging, themost widely used for the packaging of medicines are:

• PE (Polyethylene): a versatile, light, flexible but at the same time very resistant plastic material. These characteristics make it ideal for packaging a wide variety of drugs. Polyethylene can be produced in different densities and it is this characteristic that determines its end use.
• PET (Polyethylene terephthalate): is commonly used for the packaging of pharmaceutical products, in particular for the production of bottles for liquid medicines. This material is particularly resistant to the negative effects that the presence of oxygen could have on medicines.
• HDPE (high-density polyethylene) is commonly used for the packaging of solid oral dosage forms. Due to its higher density, it is stiffer and more resistant than normal polyethylene. HDPE products are particularly suitable for moisture-sensitive products, as they offer excellent resistance against water vapour.
• PP (Polypropylene): known for its robustness, resistance to heat and chemicals. Moreover, being flexible and transparent, it is often used for dosing accessories, such as scoops, spoons and syringes. In addition to these characteristics, PLA is a sustainable material and can boast one of the most established and secure recycling chains in the industry.

Irrespective of the material’s intrinsic properties, its characteristics can be further improved through the use of additives. These are substances that are added at the mixing stage to improve performance, mechanical strength or its property as a barrier against oxygen, moisture and UV radiation to the finished product. Others help to optimise the production process, such as slip additives that facilitate the processing of parts, as well as facilitating the filling phase.

Some packaging suppliers are distinguished by their high level of research in this field. One example is the development of the material Driex®, a long-lasting active layer that can be applied to the inside of containers to maintain the moisture content of active ingredients close to 0%, preventing deterioration and ensuring the therapeutic efficacy of the drug over time.

The production technologies of plastic pharmaceutical packaging

There are five different production technologies used in plastic pharmaceutical packaging:

• Compression (CM): The molten polymer is mixed inside a plasticising unit, then cut into pellets of the appropriate size and fed into a multi-cavity machine. Here, through a continuous work cycle, the material is printed and transformed into the desired item. Caps and closures are mainly produced by compression process.
• Injection moulding (IM): injection moulding is a process in which plastic material is melted and injected into a mould, which opens and releases the formed item.
• Injection-blow moulding (IBM):is a technique used to create hollow plastic objects such as bottles or containers. A jet of compressed air inflates the material placed inside a preform until it takes on the shape of the mould containing it.
• Injection-stretch-blow moulding (ISBM): compared to injection-blow moulding, the machine - in addition to the compressed air jet that inflates the object - is also equipped with a piston that stretches and elongates the product to the desired size. With this technology, bottles and pill bottles are made in various formats, also large-capacity ones.
• Extrusion (EBM): in the extrusion process, plastics - in the form of small granules - are first melted; the resulting material is then forcibly 'pushed' into a template to give it the required cross-section. A mould then encloses the material and, using compressed air, forms the item and seals the bottom.

The quality of plastic pharmaceutical packaging

The quality of plastic packaging is essentially determined by two factors: the quality of the raw materials and the efficiency of the manufacturing process. Polymers for the production of materials for pharmaceutical use have to comply with restrictive global regulatory requirements and undergo stringent testing in procurement before being used for production.

In addition to the plastic granules, continuous quality checks are carried out at all production stages, often by means of special automatic in-line viewers, which check the aesthetic aspects and the functional, mechanical and chemical tightness of the products. In addition, part of the production of plastic packaging for pharmaceutical use takes place in special controlled environments, called clean rooms, in which the continuous supervision of essential parameters such as humidity, temperature and pressure is guaranteed and the presence of particulates is limited. The air handling system is of paramount importance in these environments, maintaining the necessary sterile and aseptic conditions, as well as special access and dressing procedures.

Not only that, in order for a plastic material to be considered compliant, numerous tests must be performed to certify the material's compliance with the medicine it is to contain. For example:

• extractables: extractables are all compounds that can be extracted from the container when in the presence of a generic solvent;
• leachable substance tests: tests on those compounds that can leach from the container into the formulation of a specific pharmaceutical product, as a result of direct contact between the two.

There is a broad regulatory framework for E&L (Extractables and Leachables) evaluation, including, most importantly, the United States Pharmacopoeia (USP), the European Pharmacopoeia (EP) and FDA regulatory guidelines. USP <1663> and USP <1664>, for example, include some descriptive best practices on how to assess E&L associated with pharmaceutical packaging.

Sustainable and innovative plastics

The increasing attention to the environmental impacts of plastics has prompted the industry to seek solutions for more sustainable packaging. These include:

• Recyclable and recycledplastics: new formulations of recyclable plastics reduce the use of virgin raw materials and promote a circular approach. In addition to recyclable plastics, the use of recycled plastics, that are sometimes also recyclable, such as R-PET (recycled PET) and recycled HDPE, is becoming increasingly popular.
• Bio-based and biodegradable plastics: these include Green PE, a bio-based polyethylene made from renewable raw material obtained from sugar cane. There are materials that, in addition to being of natural origin, are also biodegradable, such as PLA (polylactic acid) derived from corn starch. These materials deteriorate naturally over time, reducing the environmental impact of packaging waste.
• Innovative plastics: products obtained by processing and reintroducing clean waste elements into the production cycle, such as bottles made from Carbon Capture PET, a special material that transforms and gives new life to CO2 emissions. This provides a dual benefit: it avoids the creation of new plastic waste material and at the same time exploits and decreases an element, namely CO2, that is harmful for the entire ecosystem.