Force requirements and insulin delivery profiles of four injection devices

Pen devices for self-injection: contrasting measured injection force with users' perceived ease of injection

OBJECTIVES

Past research has emphasized injection force as a clinically highly relevant technical attribute of pen devices. However, little work has been conducted to relate these results to in-use studies. This article explores whether and how differences in pen injection force profiles influence users' self-reported perceived ease of injection and preferences.

METHODS

Three different pen systems were subjected to measurements of injection force using an automated mechanical set-up followed by a simulated use study where users assessed perceived ease of injection.

MAIN OUTCOMES MEASURE

Outcomes were measured by fitting data of measured injection force and perceived ease of injection using a linear model.

RESULTS

Although mechanical testing revealed significant differences between the three pen's measured injection forces these differences were not directly perceived by users in simulated injection studies.

CONCLUSION

The article bridges literature on injection force measurement and simulated use. It reveals how users' perceived ease of injection is less sensitive to measured injection forces than prior research has assumed. Thus, future research should holistically integrate patient feedback in new device development. Key limitations of this work are the low number of participants in the simulated use study and the fact that the ease of injection was assessed indirectly.

Half-Unit Insulin Pens: Disease Management in Patients With Diabetes Who Are Sensitive to Insulin

BACKGROUND

Insulin pens represent a significant technological advancement in diabetes management. While the vast majority have been designed with 1U-dosing increments, improved accuracy and precision facilitated by half-unit increments may be particularly significant in specific patients who are sensitive to insulin. These include patients with low insulin requirements and in those requiring more precise dose adjustments, such as the pediatric patient population. This review summarized functional characteristics of insulin half-unit pens (HUPs) and their effect on user experience.

METHODS

The literature search was restricted to articles published in English between January 1, 2000, and January 1, 2015. A total of 17 publications met the set criteria and were included in the review.

RESULTS

Overall, studies outlined characteristics for 4 insulin HUPs. Based on their functionality, the pens were generally similar and all met the ISO 11608-1 criteria for accuracy. However, some had specific advantageous features in terms of size, weight, design, dialing torque, and injection force. Although limited, the currently available user preference studies in children and adolescents with diabetes and their carers suggest that the selection of an HUP is likely to be influenced by a combination of factors such as these, in addition to the prescribed insulin and dosing regimen.

CONCLUSIONS

Insulin HUPs are likely to be a key diabetes management tool for patients who are sensitive to insulin; specific pen features may further advance diabetes management in these populations.

A comparison study of patient ratings and safety of 32- and 34-gauge insulin pen needles

Objective

Our aims were to compare diabetic patients' evaluations of straight 32- and tapered 34-gauge 4-mm needles for usability and preference as well as the frequency of injection adverse events during insulin self-injection and to analyze the relationship between patients' preferences and their background characteristics including thumb force measured by manual muscle testing.

Methods

We enrolled 60 insulin-treated patients and measured their maximum thumb force. Patients were randomized into two groups (32- and 34-gauge) with reverse order of needle use: 1 week with one type of needle and the next week with the other. The usability of and preference for the needles were measured using the visual analog scale (VAS), and the frequency of injection adverse events was evaluated.

Results

Mean maximum thumb strength was 83.5 ± 25.4 N, tended to decrease with age and was significantly lower in females than in males. The mean VAS scores regarding smooth insertion and pain during insulin delivery were significantly different, favoring the 34-gauge needle. However, the mean VAS scores regarding ease of pushing an injection button and overall preference showed no significant difference between the two needles. There was no significant difference in the frequency of injection adverse events including breaking needles.

Conclusion

Our patients had sufficient thumb force to push the injection button regardless of needle type. Although significant differences regarding smooth insertion or pain during insulin delivery were perceived, there was no difference in overall preference between the two needles, indicating the usability and safety of the two needles are not different in clinical use.

Trigger matters: an ergonomy analysis of insulin pens

BACKGROUND

Excessive force required to deliver a set dose of insulin as well as a localization of the push button and its upwards extension may result in significant difficulties to safely perform insulin injection, including bending/breakage of the injector's needle. The GensuPen2 (Copernicus/Bioton, Warsaw, Poland) pen has a unique spring-assisted delivery system and a lateral trigger device for injection of insulin to improve its ergonomics. We tested the force required to administer insulin using three pens: GensuPen2, NovoPen(®) 4 (Novo Nordisk, Bagsværd, Denmark), and HumaPen Ergo(®) (Eli Lilly, Indianapolis, IN).

MATERIALS AND METHODS

Using a certified dynamometer we tested injection force at three doses of insulin: 2, 30, and 60 U, using each of the three injectors (n=10) in triplicate. Area under the curve (AUC) and maximum force used were calculated for each series of injections.

RESULTS

When administering doses of 2, 30, and 60 units of insulin, the GensuPen2 (6.55±1.09, 6.52±1.92, and 6.89±1.15 N, respectively) required significantly lower maximum force than the NovoPen 4 (9.04±0.61, 12.96±1.45, and 15.42±0.99 N, respectively) and the HumaPen Ergo (17.66±1.88, 32.14±6.08, and 40.39±7.64 N, respectively) (all P<0.0001). The AUC of force used for insulin injection with GensuPen2 did not differ between doses (P=0.82). At all dose levels, GensuPen2 required significantly lower force than the other two injectors. Moreover, the mode of holding of GensuPen2 was more similar to the natural arrangement of the hand while gripping a cylindrical item in comparison with NovoPen 4 and HumaPen Ergo.

CONCLUSIONS

Usage of the GensuPen2 injector with a lateral trigger location and spring-assisted delivery system reduces the force required for drug administration, especially at high doses of insulin.

Analysis: linking laboratory data to human factors and inclusion of persons with disabilities in diabetes technology research

In this issue of Journal of Diabetes Science and Technology, Friedrichs and colleagues present a study of the injection force of four reusable insulin pens and another study of the dosing accuracy of three different insulin pens. For the study of injection force, the authors claim that lower injection force has numerous advantages for patients, including making use of pens easier for people with decreased hand strength. For the study of dosing accuracy, the authors state that dose accuracy is critical for glycemic control. Both study designs have significant strengths, including measurements of the variable of interest using two different methodologies and thorough documentation of methods and materials. However, the careful, precise measurements of injection force and dosing accuracy are not matched by equivalent precision supporting the significance of the studies. The authors do not provide any information about what measured injection force is easy or difficult for individuals with and without manual problems or what level of dosing inaccuracy is clinically significant. Therefore, the implications for practice remain unclear. Data about these and other relevant human factors are needed to provide meaningful context for laboratory measurements of diabetes technologies. Furthermore, researchers conducting studies of diabetes technology that include human subjects should intentionally recruit persons with disabilities so diabetes care professionals can know whether and how technical information about diabetes technology applies to the full range of patients, including those with disabilities.

A review of 25 years' experience with the NovoPen family of insulin pens in the management of diabetes mellitus

NovoPen, the first insulin pen, was introduced in 1985. This review article is an update of a review paper published in 2006 on 20 years' use of the NovoPen family of insulin pens in the management of diabetes mellitus. The literature searches conducted in the earlier review article were updated with search results for new articles published since April 2005. This was followed by an iterative search of references cited in identified publications and by searches of abstracts from proceedings of major international diabetes conferences since 2005. Most of the original studies identified in the 2006 review showed that insulin regimens using the NovoPen family of insulin pens were at least as effective (and in some cases superior) in maintaining glycaemic control and were as safe (in terms of hypoglycaemia) as conventional insulin regimens employing vials and syringes. Most patients preferred the various NovoPen insulin pens over vials and syringes, with some evidence suggesting that the use of discreet devices, such as those of the NovoPen family, facilitates intensive insulin therapy regimens, thereby helping to improve lifestyle flexibility. The new search results showed that the current generation of the device for the adult population, NovoPen 4, retains these benefits and further meets patients' needs by improving ease of use, convenience and discretion, which may be particularly important for those with manual dexterity, visual or auditory impairments. There was also evidence that healthcare professionals would be more likely to recommend NovoPen 4 to their patients than other devices. The recently introduced NovoPen Echo, designed specifically for the paediatric population, combines half-increment dosing with a memory function that can be used to retrieve information about the time and amount of the last dose, potentially reducing the fear of double dosing or missing a dose. Evidence obtained from the new searches suggested that paediatric patients, their parents and healthcare professionals were highly satisfied with NovoPen Echo overall, with most paediatric patients rating it their favourite pen compared with other insulin pens. In conclusion, new data published over the last 5 years on the use of NovoPen devices add to the large body of published evidence supporting the patient-related benefits of durable insulin injection pens in the treatment of diabetes since the first such pen was introduced in 1985. Together, the benefits of NovoPen are considered likely to improve both patients' quality of life and their compliance with therapy.

Practical aspects of insulin pen devices

Insulin pen devices have several advantages over the traditional vial-and-syringe method of insulin delivery, including improved patient satisfaction and adherence, greater ease of use, superior accuracy for delivering small doses of insulin, greater social acceptability, and less reported injection pain. In recent years, pens have become increasingly user-friendly, and some models are highly intuitive to use, requiring little or no instruction. Despite this progress, uptake of these devices in the United States has not matched that in many other areas of the world. There is a need for improved awareness of the current characteristics of insulin pen devices among United States health care professionals. Knowledge of the design improvements that have been incorporated into pens, both to address patient needs and as a result of the improved technology behind the device mechanics, is essential to promoting the use of insulin pen devices. This review highlights some of the practical aspects of pen use and discusses the factors to be considered when selecting among different insulin pens.

Engineering study comparing injection force and dose accuracy between two prefilled insulin injection pens

OBJECTIVE

This study compared injection force (measured by glide force [GF] and glide force variability [GFV]) and dosing accuracy of the Humalog KwikPen * (prefilled insulin lispro [Humalog dagger] pen, Eli Lilly and Company, Indianapolis, IN) and the Next Generation FlexPen double dagger (prefilled insulin aspart [NovoRapid section sign] pen, Novo Nordisk A/S, Bagsvaerd, Denmark). * Humalog KwikPen is a registered trademark of Eli Lilly and Company, Indianapolis, IN, USA. dagger Humalog is a registered trademark of Eli Lilly and Company, Indianapolis, IN, USA. double dagger FlexPen is a registered trademark of Novo Nordisk A/S, Bagsvaerd, Denmark. section sign NovoRapid is a registered trademark of Novo Nordisk A/S, Bagsvaerd, Denmark.

RESEARCH DESIGN AND METHODS

A total of 100 prefilled insulin pens (50 insulin lispro pens, 50 insulin aspart pens) were tested using two dose sizes (30 U and 60 U). In all, 50 devices (25 of each type) were tested at 10 U/s dosing speed and 50 were tested at 6.6 U/s. Devices were used per manufacturer instructions. Dose accuracy (represented as absolute dose error %), maximum and average GF, and GFV data were automatically collected by the test system for all datasets (dose size/dosing speed/device type). The test system controlled for potential dosing errors.

RESULTS

The insulin lispro pen demonstrated a significantly lower median maximum GF at both dosing speeds: (2.83 vs. 3.92 lbs [30 U] and 3.00 vs. 4.14 lbs [60 U]) at 10 U/s; (1.85 vs. 2.93 lbs [30 U] and 2.14 vs. 3.02 lbs [60 U]) at 6.6 U/s, all p < 0.0001. For all datasets, the median GFV was significantly lower for the insulin lispro pen, p < 0.0001. Median dose error was comparable between device types when tested at 10 U/s dosing speed; however, at 6.6 U/s, the median dose error was significantly lower for insulin lispro pen compared to insulin aspart pen (0.47 vs. 0.67% [30 U] and 0.50 vs. 0.78% [60 U], both p < 0.05).

CONCLUSIONS

The insulin lispro pen had significantly lower median GF and GFV compared with insulin aspart pen when tested at two dose sizes and two dosing speeds. Median dose error was similar between the device types at the 10 U/s dosing speed, but median dose error was significantly lower for the insulin lispro pen at the 6.6 U/s dosing speed. A limitation of this study was that it was executed as an open label study.

A comparison of injection force and dosage scale size between NovoPen 3 and NovoPen 4

BACKGROUND

Easy-to-use insulin devices are an important tool in the treatment of diabetes. In this study, injection force requirements and dosage scale displays were evaluated for NovoPen 3 and NovoPen 4 (both from Novo Nordisk A/S, Copenhagen, Denmark).

METHODS

To simulate 5 years of expected lifetime usage, 5,475 injections were performed automatically. Before and after lifetime testing, the force required to expel 60 U of insulin from NovoPen 3 and NovoPen 4 with 30-gauge or 31-gauge needles was measured. To compare dosage scale displays, digital images of multiple settings were made, and the total inked areas of digits were converted to mm(2).

RESULTS

At baseline, the mean +/- SD injection force of NovoPen 4 was 9.14 +/- 0.87 N and 16.55 +/- 1.17 N, which was significantly lower (P < 0.001) than for NovoPen 3, at 18.36 +/- 1.06 N and 29.81 +/- 1.26 N, with the 30-gauge and 31-gauge needle, respectively. After simulated lifetime testing, mean +/- SD injection force was 10.93 +/- 0.77 N and 17.77 +/- 1.14 N for NovoPen 4, which was significantly lower than the injection force of 18.54 +/- 0.94 N and 31.69 +/- 1.98 N for NovoPen 3 (P < 0.001). The mean dosage scale digit size was 1.63 mm(2) for NovoPen 3 and 7.82 mm(2) for NovoPen 4, with a mean difference of 6.19 mm(2). The display for NovoPen 4 was 4.74 times larger (P < 0.001).

CONCLUSIONS

The mean injection force required to operate NovoPen 4 was reduced up to 50% compared with NovoPen 3 (P < 0.001), and the mean dosage display for NovoPen 4 was over four times larger than for NovoPen 3 (P < 0.001). Based on these findings, patients with diabetes who have manual or visual impairment should find it easier to dose insulin with NovoPen 4.

Recent challenges in insulin delivery systems: a review

Relatively, a large percentage of world population is affected by diabetes mellitus, out of which approximately 5-10% with type 1 diabetes while the remaining 90% with type 2. Insulin administration is essential for type 1 patients while it is required at later stage by the patients of type 2. Current insulin delivery systems are available as transdermal injections which may be considered as invasive. Several non-invasive approaches for insulin delivery are being pursued by pharmaceutical companies to reduce the pain, and hypoglycemic incidences associated with injections in order to improve patient compliance. While any new insulin delivery system requires health authorities' approval, to provide long term safety profile and insuring patients' acceptance. The inhalation delivery system Exubera((R)) has already become clinically available in the United States and Europe for patients with diabetes as non-invasive delivery system.

FlexPen and KwikPen Prefilled Insulin Devices: A Laboratory Evaluation of Ergonomic and Injection Force Characteristics

BACKGROUND

Advances in insulin pen technology continue to improve the usability of these devices for patients with diabetes. In this study, ergonomic features and injection force, as measured by glide force (GF) and glide force variability (GFV), were evaluated for the new Humalog Mix75/25 KwikPen (KwikPen) and compared with the NovoLog Mix 70/30 FlexPen (FlexPen).

METHODS

Fifty prefilled insulin pen devices (25 of each type) were measured for diameter at the cartridge holder and dose window, length and weight with cap attached, and thumb reach at 30 and 60 units. GF was also determined for 100 devices (50 of each type); GFV at 30 and 60 unit doses was calculated for the plateau portion of the force curve based on the minimum and maximum force measured in that portion of the curve.

RESULTS

While FlexPen was lighter in weight than KwikPen, and presented a slightly smaller diameter at the cartridge holder and dose window, KwikPen had a shorter overall pen length compared to FlexPen, with a shorter thumb reach at both the 30- and 60-unit dose settings. The maximum GF for KwikPen was less than FlexPen at both the 30-unit (3.42 vs 5.36 lb, p <0.0001) and 60-unit doses (3.61 vs 5.62, p <0.0001). KwikPen GFV was lower across both doses (mean difference: -0.46 lb at 30 units, -0.44 lb at 60 units; p <0.0001 for both).

CONCLUSIONS

While FlexPen was lighter with a slightly smaller cartridge holder and dose window diameter, KwikPen was shorter in length with less thumb reach than FlexPen. KwikPen also demonstrated lower GF and GFV, resulting in a smoother injection profile than FlexPen. These features of KwikPen's design and function may offer important advantages for the user during insulin administration.