Pharmaceutical companies took the promise of simple, pen-like insulin injectors for treating diabetes to new levels in devices using DuPont™ Delrin® acetal and Zytel® nylon resin as the injector pen materials.
While the devices, and challenges, are quite different, the results in these cases are clear: better devices and better treatment options.
Autopen® 2: Giving Patients More Control
For UK-based Owen Mumford company, DuPont TM Delrin® provided low friction and strength for the Autopen® 2, which improved patient comfort and provided more control over insulin dosing.
While compact insulin injectors provided convenience and simplicity, some had a significant user issue. Once a dose had been set by the user, it could not be reduced by winding the knob in the reverse direction. Instead, the user had to expel the set dose and redial. That led to wasted medications, risk of misdosing, and frustrated users.
The Owen Mumford company of Oxfordshire, England, sought to improve patient control with a patented mechanism for its Autopen® 2 insulin injector that would let users correct a misdialed dose.
The design of the Autopen® 2 lets users select a dose and press a trigger to inject the insulin. If too large a dose is selected, the button on the top of the dose selector allows the dose to be sequentially reduced to the correct level, prior to injection. But what is simple and clear for users is actually the result of sophisticated design, production and high-performance plastics.
For instance, the Autopen® 2 locking bushing, which prevents the rotational movement of the leadscrew during delivery of the medication, is molded from a toughened grade of Delrin®. This allows it to withstand high torsional forces, particularly during dose setting.
As another example, the dose knob is molded in a laser-markable grade of Delrin® for incorporation of insulin measurements. However it must also provide a robust surface for two sets of gear teeth within the part, which works with the rewind button to allow the spring to unwind as part of the dose correction procedure.
A further five parts are molded from Delrin®, including the drive gear, rewind button, dose knob cover, ratchet drive shaft and cartridge compression cup. Rigorous and comprehensive testing confirmed the compliance of Autopen® 2 with the international standard ISO 11608 for pen-injectors.
Durability is key for the Autopen® 2. It can dispense up to 72 units of insulin per injection, and is designed to be refilled with a new insulin cartridge and used again and again. The Autopen® 2 includes intricate, geometrically advanced parts that move against each other, and Delrin® offers a range of properties to support performance, including:
“Of all the plastic parts used within the Autopen® 2, seven are molded from Delrin®, and they represent all of the mechanical and robust components fundamental to its operation,” confirms Mark Eaton.
“We would not have been able to produce the Autopen® 2 without DuPont materials.”
The Delrin® products were supplied to Owen Mumford by Distrupol, DuPont’s authorized distributor of its performance polymers in the UK. Both Distrupol and DuPont provided additional technical assistance with regard to reducing friction within the dose setting and delivery mechanism.