In this article, Vinay Pandey offers tips for selecting right polymers in pharmaceutical manufacturing processes.

The world of drug formulation is very unique and complex. There are multiple types of excipients used to create stable and effective drug formulations. There are different types of excipients like solvents, antioxidants, preservative/chelating agent, pH modifiers, surfactant etc. Now to establish chemical compatibility of all the elements with single polymer is next to difficult job. To choose right polymer for the drug transfer system, one needs give consideration to factors such as chemical compatibility, pump compatibility, temperature & physical properties and biocompatibility/extractable.

Chemical compatibility

Polymer should be compatible with solvents, antioxidants, preservative/chelating agent, pH modifiers, surfactants, etc. Preservatives like BKC and benzyl alcohol tend to be absorbed by silicone, which can affect stability of drug. Same way solvents like ethanol and methanol are not compatible with silicones.

Pump compatibility

• Pump RPM: Higher the RPM, more deterioration of polymer surface. Polymer should have good abrasion resistance. Batch cycle: Longer the batch cycle, more flex stress tends to generate on polymer tubings.
• Flex crack Resistance: High flex crack resistant polymer tubings last long in pump applications.
• Low Spallation: Spallation is measure of amount of material loss in grams after completion of pump trials.

Temperature & physical properties

• Service temperature: Polymer should withstand fluid temperature and typical sterilisation temperature (121°C)
• Surface properties: Polymer surface should not promote bacterial growth.
• Biocompatibility/extractable
• Elemental impurities: Polymers formulations should be kept to meet ICH Q3D heavy metal limitation guidelines.
• ISO 10993: Ideal polymer should compatible with basic biocompatibility standard like cytotoxicity, Pyrogen tests.
• USP standards: It should meet USP 87 and 88 requirements.
• VOC, SVOC, NVOC: There should be low volatile (VOC), semi volatile (SVOC) and non-volatile contents (NVOC).

Selecting the right polymers

Elastomers, thermoplastic elastomers and plastics are the three basic categories of polymers most widely used in pharma industry. Table 1 shows characteristics of various polymers used in pharma industry.

Polymer industry is placing its hardest efforts to meet pharma and biotech regulatory requirements. Other polymers like butyl, EPDM and PVDF are also in demand among biopharma industry. After strict recommendation of ICH Q3D guidelines in pharma industry, formulation scientists must refer to Table 1 of polymer selection index for selection of right polymers.

Vinay Pandey (Rubber Technologist) is Manager - Business Development at Ami Polymer Pvt Ltd - a sealing expert in silicone.

Table 1: Polymer selection index