Biomedical News

Simulating Real World Use of Auto-Injectors to ISO 11608-5

Testing needle-based injection systems, or auto-injectors, is most commonly tested based on ISO 11608. The standard specifies requirements and test methods for these combination drug device products. While there are seven annexes within the standard, ISO 11608-5 identifies the requirements for testing the product in its final use case. The final use case of an auto-injector entails a patient removing the auto-injector safety cap, positioning the injector, and pressing down on the device to inject the drug. The injector is designed to automatically release the accurate dose of medication in the appropriate time. Both manual action made by the patient and the automatic functions of the auto-injector must be quantified during a test, which can lead to cumbersome test setups, customized software programs and, in some cases, multiple computers or data acquisition systems. In order to streamline testing of needle-based injection systems, Instron offers an integrated testing system that enables users to measure the following:

  • Force to remove the safety cap
  • Activation force and displacement of the auto-injector
  • Injection time
  • Weight of the drug volume using an integrated scale
  • Effective length of the needle during injection using a camera system
  • Force to displace the needle guard

Instron’s integrated test system allows for all required testing to be carried out in a single test method for each individual auto-injector. In some cases, an entire test can last under one minute, depending on speed, dose, and product requirements. Despite the complexity of needle-based injection systems and the testing requirements, simplifying the test method into a single test helps users ensure the accuracy of results and simulate real product use cases, while saving time.

20 Ways to Test a Syringe [Upcoming Webinar]

Join Instron Biomedical Market Manager Elayne Gordonov to learn 20 different mechanical tests for syringes that may be required to ensure the device meets quality standards. This webinar will cover testing solutions for pre-filled, hypodermic, single-use, and needle-based injection systems as required per:  

  • ISO 11040-4
  • ISO 7886-1
  • ISO 8537
  • ISO 80369-20
  • ISO 11608

We are offering two webinar times on October 18 to reach our global audience. Register for the viewing that best suits your time zone:

 9:00 AM EDT (1:00 PM GMT)    | Register  

2:00 PM EDT (11:00 AM PDT)    | Register  

Auto-Injector Spring Simulation with an ElectroPuls System

The auto-injector has become an attractive choice for patients and doctors alike who wish to save time and reduce effort. These injections do not need to be overseen by a doctor or GP, and therefore can be performed in the comfort of the patient’s home. This is an especially important option for patients needing to inject medicine frequently, like diabetics.

Auto-injectors are spring-loaded syringes containing a prescribed amount of drug for the patient to perform subcutaneous injections. The device itself if easy to carry and load, with the general design consisting of a single activation button, which the patient must press and hold for approximately 5 seconds while the needle is inserted into the thigh or buttocks. There are also status indicators to ensure all of the drug has been released. The needle generally stays quite hidden, making the procedure less intimidating for the patient.

The abovementioned design features all help to increase comfort and safety, but the most critical variable is delivery time. Factors affecting delivery time include the drug viscosity, needle diameter, and the lubricant used. The delivery time can be optimized by choosing the appropriate spring and preload for a given syringe/drug system, which is currently achieved by subjecting springs with varying degrees of stiffness to different loads. However, testing a large number of springs is very time consuming and expensive for medical device companies. This presents the need for a method of moving through this iterative auto-injector design process more quickly. Instron’s solution to this challenge bypasses the need to test multiple springs by utilizing the ElectroPuls’ advanced control capabilities to produce a unique spring simulator. This significantly reduces the required design time. By building on the core capabilities of the ElectroPuls, the 8800 controller and WaveMatrix software, Instron was able to simulate these complex interactions within the spring/syringe system with just two inputs.
 
 Drug Delivery System 

Simulating a Spring

Typically, material testing instruments are required to move as a function of time. For example, a simple tensile test might be specified in mm/s, or a cyclic test in Hz. This presents a challenge when attempting to simulate a spring, as the applied load is usually known as a function of position. Additionally, since injection time is an unknown output of the simulation, it is not possible to calculate the force/time function for a given spring.

Instron solves this control challenge using Modal Control, an advanced feature of the 8800 controller that creates a composite channel to allow the applied load to vary with actuator position. The user simply needs to specify the initial preload and spring stiffness for the system to adjust itself, based on the actual load seen by the syringe. The resultant load and system displacement data is acquired by the 8800 controller at a rate of up to 5 kHz. A force versus time graph is produced (see graph B below), from which the Calculations Module feature in WaveMatrix then determines the dispensing time and stall force of the syringe. The user can then determine if the chosen parameters for spring stiffness and preload have yielded an ideal auto-injector dispensing time for a given drug.

Graph A below illustrates applied load with respect to the actuator position as the ElectroPuls moves downward to dispel the drug through the syringe. Graph B depicts the injection time (about 6 seconds for this particular syringe/drug system) in the form of a load curve (red) and displacement curve (blue). As you can see, the displacement over time is fairly linear, which shows that the drug is being released at a fairly consistent rate. The speed is reasonably consistent, even as the load decreases.
 

Auto Injector Spring Simulation Graph

Testing Pre-filled Glass Syringes to ISO 11040-4

As pharmaceutical companies seek more convenient drug delivery methods, pre-filled syringes have emerged as the preferred choice. Pre-filled syringes make injections easier and safer for nurses, doctors, and patients. Pre-filled glass syringes are most commonly tested to ISO 11040-4. As glass syringes are more susceptible to brittle failure than plastic syringes, there is a wider variety of tests required to be performed on them. ISO 11040-4 has a total of 10 annexes, each requiring a different mechanical test. The annexes in ISO 11040-4 are as follows:

  • Annex C.1 for flange braking resistance
  • Annex C.2 for Luer cone breakage
  • Annex E.1 for glide force
  • Annex F.1 for needle penetration
  • Annex G.1 for needle pull-out force
  • Annex G.2 for liquid leakage testing
  • Annex G.3 for Luer lock collar pull-off
  • Annex G.4 for Luer lock collar torque
  • Annex G.5 for Luer tip cap unscrewing torque
  • Annex G.6 for pull-off force of the needle shield

While glass syringe manufacturers or pharmaceutical companies only need to test the annexes that are applicable to their end product, many companies are required to follow all of them. In order to simplify the test system required to perform both axial and torsional tests, and to simplify the number of fixtures needed to meet all annex requirements, Instron offers the Torsion Add-On for all 5900 table top systems in addition to modular fixtures that can be combined to meet all testing requirements in ISO 11040-4. The Torsion Add-On is a modular design that enables users to add a rotational capability to their traditionally axial-only 5900 system. Instron’s ISO 11040-4 fixture utilizes common parts that are integrated with each other to simplify load string changes. In addition, all fixtures are suitable for the diameter and length ranges as specified in the standard.

ISO 11040-4 Breakage Resistance
ISO 11040-4 Needle Shield

 


Efficient QC Testing for Vial Cap Leaks

While visiting a company that produces glass vials for the dental industry, the customer explained how their QC testing for potential cap leaks was becoming a huge bottleneck in their manufacturing process. They were required to test a certain number of caps per lot of vials, and their testing process was laborious, manual, and time consuming. They turned to Instron to come up with a more efficient approach.

Solution:

The solution that Instron created utilized our AT2, automated XY Stage System, fitted with a custom, stainless fixture to hold a large batch of specimens, complete with a removable, polycarbonate drip tray to catch any fluid from leaks. Using the TestProfiler package from the Bluehill® material testing software, Instron was able to develop a custom test that checked for vial cap leaks at a variety of required loads, clearly marking each test as a pass or fail.

 

Automated XY stage


To satisfy 21 CFR Part 11 compliance, ComplianceBuilder was installed on this system. Working side by side with Bluehill and the automation control software, the complete system package met all of the customer’s requirements and reduced their testing time by 66%.

 

Bio Days [Coming Soon]

Keep an eye out for the upcoming Instron Bio Days, a new biomedical focused event series that we’ll be hosting at a wide variety of medical device companies through the end of the year. This will be your chance to learn about…

  • Challenges with regulatory requirements and testing
  • New Instron services for medical device manufacturers and researchers
  • Trends in biomedical services and testing

Find out when we’ll be at your facility - contact us for details.