Understanding the evolution of container closure integrity testing

At different stages of the drug lifecycle, the minimum provision for parenteral products is a safety barrier against potential contaminants. This protection is guaranteed by selected container closure systems, whose aseptic packaging performs broad roles like shielding freeze-dried products against water vapour, guarding vaccines from temperature fluctuations, preserving biologics against photodamage, or otherwise stabilising drug properties.

Historically, these packaging systems were developed by manufacturers after stages of unregulated trial and testing. However, it wasn’t until 2008 that the US Food and Drug Administration (FDA) codified container closure and integrity testing (CCIT) as a requirement to preserve product sterility.

But, while guidelines stipulate that packaging systems provide adequate cover against impurities, they do not specify preferred testing methods to achieve this feature.

However, as the pharma industry evolves into a modernised and precise landscape, manufacturers are entering what promises to be the next phase of packaging testing, marking a shift from probabilistic to more deterministic evaluation methods.

History of CCIT

Widespread recognition of closed container integrity testing began in 1998, when the FDA published its notice “Container and Closure Integrity Testing in Lieu of Sterility Testing as a Component of the Stability Protocol for Sterile Products” as an informal guide on testing protocols.

Although recognised, these official testing notices had limited impact, as manufacturers accepted packages simply as the container to deposit and transport newly developed drugs. This period credited time- and labour-intensive sterility tests as the gold standard to determine if a pharmaceutical product maintained a sterile barrier against microorganisms after manufacture and packaging. Steadily, widespread appeal grew for container closure integrity testing after direct lines were discovered between packaging integrity and product shelf life, plus improved patient safety.

In particular, CCIT rose to prominence following limitations of sterility tests, such as false positive readings from testing-induced contaminants, as well as the damaging nature of sterility tests to the drug product tested.

Official recognition for container closure integrity testing began in 2008, when the FDA published the actual Container and Closure Integrity Testing in Lieu of Sterility Testing as a Component of the Stability Protocol for Sterile Products protocol. This guidance stamped CCIT as the preferred measure for assessing medical and pharmaceutical product sterility.

However, despite receiving official acknowledgment, preferred CCI testing methods remained uncertain until the United States Pharmacopeia (USP) released clarifications on this issue, via the USP guidance 1207 ‘Package Integrity Evaluation-Sterile Products’.

CCIT testing methods

Product quality and stability assurance has seen a gradual progression from early visual-based strategies within the package testing space. These conventional, probabilistic strategies offer indirect evidence of packaging integrity, relying on departures from expected packaging behaviour to expose defects, rather than a direct analysis of integrity lapses.

Dye ingress

The dye ingress test assesses container closure integrity through a visual evaluation of any leaks or openings in the closure system. This process requires the submersion of the container and control package beneath a dye solution. Both packages are then subjected to rounds of pressure, the first being vacuum pressure before a return to atmospheric pressure, following which additional atmospheric pressure will be introduced to determine packaging integrity.

Where there is visible staining or discoloration in the packaging, this can indicate a compromised barrier, meaning the container has failed the test. Where the system shows no signs of dye penetration, the closure system is intact.

Bubble emission leak test

The bubble emission or leak test detects leaks by exposing bubbles after submergence. The bubble emission or leak test also takes a visual approach to detect leaks in product packaging. Using this method, the product package is submerged in water, before a vacuum or pressure is applied to the system. This external pressure permits air or gas to escape the packaging, indicating the leak location.

Microbial immersion

Microbial immersion is ideal to identify whether a container system is able to prevent the ingress of microorganisms from the environment. By exposing the container to microorganisms and intubating for a time period, manufacturers can determine if contaminants have breached the packaging structure.

On one hand, probabilistic measures are ideal controls for low-value products like paracetamol, which do not require high-end testing methods to determine stability. However, this method can prove expensive and inefficient, as the destruction of the product during testing can limit future use or investigation for cause of failure.

The subjective nature of these tests also leaves results prone to human error and free discretion. Likewise, these strategies require detailed preparation processes and expertise from technicians in charge of the process.

Over time, the manufacturing landscape has transitioned from uncertain probabilistic methods, to more reliable and accurate deterministic strategies. The 2016 USP Chapter 1207 sealed this move stating: “A deterministic leak test method having the ability to detect leaks at the product’s maximum allowable leakage limit is preferred when establishing the inherent integrity of a container-closure system.”

Deterministic testing methods

Deterministic methods are a move towards the modern ideal for container integrity testing. Already, stakeholders are transitioning to these accurate measures, with a 2021 Pfeiffer Vacuum poll revealing 34% of participating manufacturers combine blue dye ingress with deterministic methods to determine packaging stability.

While regulations direct deterministic methods for leak testing, manufacturers are to ensure the selected technique is capable of meeting specific requirements - whether this is heightened sensitivity to detect smaller defects in packaging, easy implementation, or quick, real-time feedback in high-volume test environments.

The following are deterministic processes to observe a closure system’s ability to maintain a sterile barrier against foreign threats:

Electrical conductivity and capacitance test (HVLD)

This assay identifies container leaks using the power of electric charges. The HVLD principle applies a high frequency charge outside, within, or in close proximity to the sample marked for testing.

Where there are defects in the packaging system, a change in electrical conductivity will signal a leak in the vicinity of the disruption. Leak-free packages will emit low voltage readings, providing feedback on the integrity of the container closure against contaminants.

Headspace gas analysis

Headspace gas analysis explores the gas concentration of the sealed container to determine if external entrants have seeped into the drug product.

This analysis introduces gases like nitrogen, carbon dioxide, water vapour, or pressure into the container headspace, utilising the compound effects of light and gas to evaluate package stability.

By first introducing gases into the container headspace, then passing light via a diode laser into this region, manufacturers can detect any changes in gas concentration and pressure. This testing system is highly sensitive to small leaks and is suitable for products encased in vials and ampoules.

Pressure decay

Pressure decay testing is determined through the movement of gas from the outside to the inside of the product contained in the closed container system.

By placing the container in a fixture that is pressurised to a target level, any pressure loss is a certain indicator that the container is experiencing a leak. Pressure decay is the measure of choice for oil-based, viscous, or lyophilised products.

Mass extraction

Using mass extraction, the unit under test is placed into a vacuum test chamber or other controlled environment where gas flow is directly measured to identify potential leaks.

Technicians are required to monitor the airflow to determine if there are any changes in container mass after specified pressure is introduced to the test chamber.

Relevance of shifting trends in CCIT

The advancement of container testing into more deterministic systems marks a turning point in pharma manufacturing processes.

By offering highly sensitive measurements of packaging defects, manufacturers are at an advantage to detect early on any potential issues in the production process, limiting chances of recall.

Through deterministic testing methods, organisations can enhance quality control to deliver safer and more reliable products to consumers.