Syringes are classified as medical devices that play a critical role in the delivery of drug products in a safe manner and at very precise dosing levels. The syringe must perform as expected at all times and manufacturers and packagers of the drug product must perform the necessary qualification testing to understand the impact that the product, package components and processes, storage, and agitation may have on these systems. The ISO 7886-1 standard regulates the mechanical properties and defined specifications of drug product syringes while also including guidelines related to the design, manufacture, and functionality of them. ISO 11608-3 for needle-based injection systems similarly outlines requirements. Break Loose (initiating) Force and Glide (sustaining) Force are two critical and common functionality tests that are routinely used for testing and qualification purposes.
Break-Loose Force, or initiating force, is defined as the amount of maximum force required to dislodge the plunger from its resting position in the barrel of the syringe. Glide Force, or sustaining force, is defined as the force required to maintain plunger movement once static friction has been overcome. Ultimately, the force required to expel liquid from the syringe must be small enough to ensure that any medical professional or end-user patient can perform the task without resistance, but not so low that there is a risk of unanticipated plunger movement.
The most effective approach to qualifying a syringe specific to Break Loose and Glide acceptable standards utilizes a single column Instron instrument with a custom designed syringe sample fixture. Because the forces involved are relatively small, a 100 N or 50 N load cell is preferred. This test measures this attribute of a syringe barrel-plunger seal by simultaneously applying a perpendicular force to the syringe barrel and maintaining a constant compressive force on the syringe plunger. The force profile typically displays an initial peak force known as the break loose force, and an average force of the remaining plunger travel, known as the glide force. This test also requires the recording of maximum force during plunger travel excluding the break loose force.
The CS Analytical Team has been developing, validating and implementing Break Loose and Glide protocols based upon ISO 7886-1 and 11608-3 guidelines for more than twenty years and has the knowledge and experience to ensure your syringe system meets design intent.