ISO 11608-1:2014 Needle-Based Injection Systems
Mechanical Testing of Autoinjectors
ISO 11608 is a testing standard that describes the functional requirements for needle-based injection systems (NIS). It is critical that biomedical manufacturers perform thorough testing of these devices during development and production, due to their importance in delivering medications. As possibly the most extreme example, autoinjectors deliver immediate lifesaving intervention in the case of anaphylaxis, and cannot afford to fail.
ISO 11608 aims to ensure that the device reliably performs the minimum activation and operation steps to meet safety requirements and to be reliably operated by various users. This typically includes the following evaluations:
- Cap removal/Priming Force
- Activation Force
- Injection Time
- Dose Accuracy (Referencing ISO 11608-1)
- Effective Needle Length During Injection
- Needle Shield Override (If using passive safety device)
- Confirmation of Operation (Automated functions require either visual or audible indication for the user that they have completed)
The 'needle injection systems' definition includes single and multi-dose syringe or cartridge-based systems. These devices can also be generally referred to as combination products, combining a syringe or cartridge with a mechanical device to administer the medicine. Furthermore, the devices can also be single-use or reusable. Consumers are most likely familiar with the terms "autoinjector" and "pen injector," where autoinjectors are typically a single-use single-dose device most commonly associated with epinephrine treatment of anaphylaxis, and pen injectors are typically a multi-use reusable device associated with treatment of chronic diseases like diabetes.
Instron has developed a single column 6800 Series testing system with an autoinjector test fixture to provide repeatable and reliable results. Utilizing a single system to sequentially test all the parameters outlined in ISO 11608-5 provides more consistent test results and simplifies data collection and analysis. Laser measurement of injection time provides the most reliable results, regardless of fluid viscosity.
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Instron 68SC-1 Testing System
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Bluehill Universal Software
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2580 Series Load Cell
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| Auto-Injector Test Fixture | |
| CP130106 Cognex Camera Display | |
ISO 11608 includes subsections addressing the various subcomponents and functionality of the overall device:
- 11608-1 outlines the general requirements for these devices and the assessment of dose accuracy and efficiency. These metrics are by far the most crucial, having the greatest direct impact on the efficacy of drug delivery.
- ISO 11608-2 is specifically related to attachable needles used on cartridge-based systems. Syringe-based systems will typically see the needle staked onto the end of the device at the time of manufacturing. This evaluation will mainly quantify the torques required to assemble and disassemble the needle hub from the NIS. In addition, the bond strength between the needle and hub will also be required to verify the design of the needle component.
- ISO 11608-3 addresses the requirements for the containers used within the NIS. The forces necessary to initiate and sustain movement of the plunger are required to ensure repeatability of the delivered volume. The spring-based mechanism which interacts with the plunger will be designed to exert a specific force over the required travel, meaning a container with higher-than-specification break loose characteristics may not dispense the full volume, resulting in a rejected batch.
- ISO 11608-4 mainly discusses the electronic components of NIS devices, not necessitating mechanical testing.
- ISO 11608-5 assesses the automated functions and user interaction with the NIS, looking at the device rather than the individual components. This section is particularly vague in describing the test requirements, considering that the overall device design can vary greatly depending on the target user and medical use case. Devices designed for use on the battlefield as a nerve agent antidote will be evaluated using the same standard as a typical insulin pen.
- While still a draft, ISO 11608-6 is being developed to address the unique testing requirements related to wearable injection devices. These devices will delivery larger volumes of medicine over longer periods of time and use medical grade adhesive to maintain device contact with the patient’s skin for the duration of the injection. Testing these devices includes activation force and dose accuracy requirements like pen style devices. The time factor complicates the injection time assessment, now requiring an evaluation of the dose profile, ensuring the dosage rate stays within certain boundaries. The adhesives used on the devices also need to be tested extensively, confirming they maintain appropriate contact between the device and the patient throughout the injection.
- To read the specifications for each test method, purchase ISO 11608:2014
- To learn more about the mechanical testing of drug delivery devices and containers, click here.
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Semi-automated Auto-Injector ISO 11608-5
Instron's semi-automated auto-injector test fixture is designed for use with the 6800 and 5900 test systems and Bluehill® Universal Software with the TestProfiler module, which allows the system to measure cap removal, activation force, injection time, injection mass/volume, and lock out force of the needle shield in a single test method.