Ph. Eur. Update on Rubber Closures

A revised version of the Ph. Eur. chapter 3.2.9. Rubber closures for containers for aqueous parenteral preparations, for powders and for freeze-dried powders has been published in Pharmeuropa 37.4. The comment deadline is 31 December 2025.

Background and Changes

Rubber closures are made from elastomers and include stoppers for vials, sealing disks and plunger stoppers for cartridges, as well as rubber tip caps, needle shields and plunger stoppers for syringes, etc. Coated closures consist of a bulk of rubber, bearing on its surface (or a part of it) a layer of a different polymer. Bi-layer seals are composed of 2 different layers of rubber: one layer exhibits a higher level of chemical purity and is intended for contact with the pharmaceutical preparation, and the other layer presents greater elasticity and is intended to improve self-sealing and fragmentation resistance of the seal. The closures are usually washed and may be (pre-)sterilized before use.

The following sections have been revised:

• Reducing Substances: For better clarity, the volumetric solution (0.01 M sodium thiosulfate) used to calculate the difference between the volumes used in the two titrations is now mentioned.
  
  
• Extractable Zinc: The analytical procedure has been modified to clarify that acidification of the sample solution is always required to ensure accurate determination of zinc by AAS.
  
  
• Fragmentation: The term ‘rubber’ has been replaced with ‘closure’ to clarify the requirements also apply for coated and bi-layer closures.

Lubricated closures comply, in their lubricated state (e.g., treated with silicone oil), with the requirements defined in this general chapter. However, this chapter does not cover closures made from silicone elastomer. Requirements for silicone elastomer used for the manufacture of closures are dealt with in Ph. Eur. chapter 3.1.9. Silicone elastomer for closures and tubing.

For more information please visit Pharmeuropa online.