A Container Closure Integrity Test Method for Vials Stored at Cryogenic Conditions Using Headspace Oxygen Analysis

Abstract

An increasing number of pharmaceutical products require deep cold storage at cryogenic conditions, approximately -150°C to -190°C, to maintain stability and/or activity. Previous work has revealed that, at these extreme conditions, a typical pharmaceutical package configuration (vial, stopper, crimp cap) may lose container closure integrity (CCI) due to both the glass transition temperature (-55°C to -70°C) of the rubber stopper used to seal the vial and the different thermal expansion coefficients of the primary packaging components. Importantly, this type of temporary breach in CCI frequently reseals itself when the vial is brought back to ambient temperature. The following study illustrates a CCI test method for identifying both temporary and permanent defects in vial assemblies exposed to cryogenic storage conditions using laser-based headspace oxygen analysis. The method takes advantage of the nitrogen-enriched environment that exists in most cryogenic storage conditions. When vials are placed into cryogenic storage, the cold temperature creates a pressure gradient across the vial seal that, if a leak defect develops, drives nitrogen gas into the vial headspace and, thereby, decreases the headspace oxygen concentration for vials originally packaged with an air headspace. This decrease in headspace oxygen after the cryogenic storage period can be used to identify a breach in CCI, regardless of whether the defect is temporary or permanent. Experimental data obtained for three different vial types (a 2R glass vial, a 2 mL plastic CZ vial, and a 2 mL plastic Aseptic Technologies (AT) vial) demonstrated that this CCI test method can robustly and readily detect laser-drilled micron-sized positive controls down to 5 μm (the smallest defect size tested) in the body of the vial and type controls prepared using a Ø64 μm wire at the stopper-seal interface (effective defect size varied depending on the vial).