Vial Stopper : which quality standards should you require to secure your filing process ?

Although rubber vial stopper manufacturers are numerous around the globe, their quality standards are not equal. Beyond the obvious chemical compatibility issues between rubber and formulation which will be secured by your laboratory, we want to highlight the issues you may face even with good quality rubbers.

Why compatibility between the rubber plug stopper and the formulation is mandatory but not enough ?

The rubber plug being in contact with the formulation (fluid or powder), most if not all pharmaceutical companies will have a robust compatibility test protocol to secure and insure a neutral impact of the rubber on to the formulation. This protocol will usually analyse chemical migration, color dilution, mechanical properties to secure the sealing.

Focusing mainly on the pharmaceutical aspect may not be sufficient and should be supported by several major filling and usage aspects which may not always be the priority. Any shortcut in this matter may jeopardize the entire filling process and consequently the medicine.

Which aspects of the Vial Stopper you may want to control upfront ? 

You may of course already have some if not most of the below criteria already in place, but in order to make sure you cover all aspects, we’ve split in three major categories.  

Chemical properties of the stopper

Rubber material must have the proper chemical composition, either through an extracibles/leachibles profile which is compatible with your drug or through protective films, applied on the surface of the stopper parts in contact with your formulation.

In this regard we recommend you scrutinise and double check the validity of any certificates you are being given.

Mechanical and physical properties of the stopper

The purpose of a vial stopper should be to protect the content on a long term basis and deliver easily when the content is extracted from the vial. 

The elasticity and mechanical memory of the rubber stopper during the whole shelflife of your valuable drug is key to secure the sealing with the vial despite any variation of temperature and time length of contact with the formulation. Accelerated ageing tests in vacuum chambers at high and low temperature are in place to secure this aspect of the product development. These mechanical properties should also ensure that the pressure provided by the aluminum crimp cap remains the same all product life. Indeed, a small variation of the elasticity of the rubber stopper may open a leak path. Also, the stopper shall resist to a certain number of piercings by needles or spikes and avoid that rubber-fragments pollute the liquid (so-called “coring”).

Last but not least, in use, the vial stopper must remain extremely safe whatever routine is operated to get the fluid or the powder out of the vial. Unplugging manually should be convenient, piercing with a needle should be safe. In any situation, the integrity of the rubber mechanical properties should remain stable. 

Aesthetic properties

This aspect may seem insignificant, but it should be considered as an indicator of quality. Indeed, a permanency of the aesthetical properties (shape, color and the absence of black, white or yellow spots, indicating the unperfect mixing of formulation compounds such as talcum, carbon-black or sulphur… ) is clearly a visible indicator of the stability of the packaging material. We recommend that your vial packaging offers an eye view of the rubber stopper which offers the possibility to make a visual check of its integrity.

Our recommendations to offset the above-mentioned risks, secure your filling and overall manufacturing process

We highly recommend to include these quality aspects from day one of the plug supplier selection process. Having the production / filling staff included in the selection process is a must but still missing in some firms.

Amend your vial stopper supplier selection process 

One of the most productive and participative approaches is to proceed with a specific internal survey to capture the issues related to the vial stopper. Collecting this valuable information from all departments and individuals in contact with the item will secure that the amendment of the selection process covers all your specific needs.
As an example and depending on your filling process, some aspects could be checked such as the static electricity charge of the plug, the non-stickiness of the rubber plug and much more.

Inquire your flip off cap supplier who may have a large experience to share 

Aluminum crimp cap manufacturers do have many contacts with rubber vial stopper manufacturers . Shall you have a positive and constructive sourcing experience with them, they will most probably share it as it will have a direct impact on the crimping process.

Duplicate your sourcing to secure filling activity but not only…

Even if it might seem to be a long road to go again through necessary stabilities, adding a second or a third source of vial stopper is worth not only logistically to avoid an out-of-stock situation. The benefits for your organisation go far beyond the obvious sourcing flexibility gains if you look at it from a bench mark or swot perspective. Indeed, experimenting with a new supplier will open some new challenges and most probably some positive aspects you wouldn’t have thought about with your current supplier installed in a routine service towards your firm. 

To conclude

In conclusion, we hope we have given you the opportunity to rethink your existing vial plug/rubber stopper  selection process. Looking at it from another perspective is always worth making the right decisions. 

Far from being a commodity item, this specific packaging is a key element which should connect precisely with the vial and with the aluminum crimp cap to secure the aseptia of the formaluted content. This small packaging material has a major added value and a high responsibility within the entire lifetime of your pharmaceutical formulation.

Now that you have all in hand to control all major and minor aspects of the rubber vial plug. We hope we’ve helped you to check your quality product and supplier selection process. 

We will be happy to support more if needed and share our experience with you on request.