Analysis of “Dose Accuracy, Injection Force, and Usability Assessment of a New Half-Unit, Prefilled Insulin Pen”

Abstract

Half-unit insulin pens (HUPs) offer finer gradation of insulin dosing than their integer-unit counterparts, tackling the inaccuracies of dose rounding that make it difficult for insulin-sensitive populations to achieve tight glycemic control. This article analyzes the first prefilled HUP, the Humalog Junior KwikPen, in the context of other, similar devices and the developing landscape of smart insulin pens. The Junior KwikPen’s suitability for pediatric patients is assessed in reference to a recent study surveying its accuracy and usability under varying conditions intended to simulate real-world use.

Diabetes stands out among chronic diseases for the high level of individual management it requires. Tight glycemic control is critical to prevent long term diabetes-related health complications, but needs effort and commitment that can detract from overall quality of life.^1,2 Minimizing this overhead can give patients a better chance at managing their diabetes while leading full, unencumbered lives. Insulin pens are a key technological advancement toward this goal. Whereas traditional syringe and vial systems of insulin delivery are often associated with pain, inconvenience, and social stigma, insulin pens offer a more comfortable and discreet alternative.^3,4 Critically, they tend to be more accurate than syringe systems due to incremental dose dialing capabilities.^5,6 This greater reliability and flexibility of insulin pens improves the chance of patient adherence to prescribed insulin regimens, potentially making diabetes management both more convenient and effective.

For pediatric patients and other cohorts particularly sensitive to insulin, precise dosing is critical.⁷ However, many first-generation insulin pens do not allow dose dialing in small enough increments to accurately deliver the calibrated amount. Half-unit insulin pens (HUPs) tackle this problem by reducing the minimum dose volume and allowing higher resolution dialing than their integer-unit counterparts, reducing the inaccuracies of dose rounding. Several HUPs have been introduced into the market in recent years with the aim of making glycemic control more accessible to insulin-sensitive groups.⁸ Eli Lilly’s newest product, the Humalog® Junior KwikPen®, offers an added benefit: as the first prefilled HUP, it eliminates the need for users to load an insulin cartridge themselves. This is particularly useful for children and the elderly who may have limited manual dexterity or trouble dealing with more complex reusable systems. In these cases, the prefilled HUP involves fewer steps for simpler, more intuitive use.

The Junior KwikPen is designed with young users in mind. The pen is lightweight and shorter than many other devices for easy transport and handling, and the force that must be applied to the injection knob is comfortably exerted by children.⁹ To minimize the pain and psychological toll of conducting an injection, the duration the needle must remain in tissue is relatively low at 5 seconds. Several dose-dialing features employed by other KwikPen devices are included in the Junior KwikPen to reduce the risk of incorrect dosing.^10,11 These include audible clicks upon dialing each half-unit increment, a clear viewing window to see the dialed amount, and a dial-back feature that lets the dose be lowered without dismantling the pen or discharging any insulin. Furthermore, the pen supports a “sanity-check” feature that prevents a dose larger than the available insulin volume from being dialed. These functionalities are geared toward making injection more intuitive and error-free. The limited number of preparatory steps compared to reusable half-unit pens, combined with a simple interface, promises greater autonomy to children learning to self-administer insulin.

To confirm the Junior KwikPen’s suitability for insulin-sensitive patients, Kappes et al test the device’s performance under conditions intended to simulate real-world use by target cohorts. A usability study involving a mock injection task was conducted on participants including pediatric patients and adult caregivers. The overwhelming majority of participants—including an untrained subset—successfully completed the simulated dose dialing and injection, confirming the device is simple and intuitive to use. Kappes et al conduct additional statistical tests to investigate how dose accuracy is impacted by different pen fullness levels, dose sizes, ambient temperatures, and simulated rough use involving vibration and free fall. Accuracy remained well within clinical standards across these test conditions, demonstrating the Junior KwikPen’s utility as a portable, easy-to-use insulin delivery system robust enough for younger patients’ daily use.¹²

To validate the clinical significance of the Junior KwikPen, and indeed HUPs in general, further work is needed to test whether these devices favorably control A1C levels and reduce periods of hypoglycemia.⁸ Population studies must be conducted to determine whether the refined dosing and simple operability of the Junior KwikPen actually translates into fewer missed doses and better glycemic control for insulin-sensitive groups. The cost of insulin therapy is another practical aspect that must be considered for new devices when gauging their potential for broader impact. Integer unit pens are more expensive than traditional syringe and vial systems, but these initial expenses can be offset by the reduction in health care costs associated with hypoglycemia, including costs of emergency hospital visits and treatment.^13,14 Further studies are needed to determine whether switching from integer unit pens to HUPs has similar financial effects, both in terms of reducing insulin wastage and hypoglycemia counts. Investigating the Junior KwikPen’s impact on glycemic control would thus give dual insight into its physiological and financial benefits.

For the majority of patients with diabetes who do not use insulin pumps, including a large portion of the pediatric community, advances in insulin pen technology can have high impact on quality of life.¹⁵ Recent developments in HUPs include a Bluetooth-enabled pen and custom app that track insulin dosage over time and provide a dose calculator to reduce the guesswork of determining how much insulin to inject.¹⁶ In the future, it is likely that insulin pens will become increasingly “smart,” integrating big data techniques with detailed longitudinal tracking of health indicators to make more accurate and personalized dose suggestions. These pens will further enable dose information to be digitally relayed to health care providers, allowing physicians to monitor missed doses and overall patient adherence to insulin therapy. Since dose accuracy and compliance with treatment both heavily impact glycemic control, these next-generation pens will likely make diabetes management more effective and accessible.¹⁷ However, for such technological advancements to be useful across the diabetic spectrum, including for insulin-sensitive pediatric patients, insulin pens will still need to ensure intuitive interfaces, easy usability, and fine dosing increments. By focusing on these fundamentals, the Humalog Junior KwikPen demonstrates that young or new users remain a focus in the developing landscape of insulin delivery technologies.