A comparison of the handling and accuracy of syringe and vial versus prefilled insulin pen (FlexPen)

BACKGROUND

To determine the preferable method for self-injecting insulin, we compared the handling, safety, and dose accuracy of a conventional disposable syringe and vial with FlexPen (Novo Nordisk A/S, Bagsvaerd, Denmark), a prefilled pen.

METHODS

Insulin therapy-naive healthcare professionals (HCPs) (n = 30), unfamiliar with insulin delivery, injected 10 U of insulin into a sponge pad using either a syringe and vial or the FlexPen, both with 30-gauge 8-mm needles, on day 1. The following day, they used the alternative method. They evaluated the handling of the two methods on device-specific questionnaires and compared overall preference on a third questionnaire. To evaluate dose accuracy, 30 insulin therapy-experienced HCPs and 20 insulin therapy-naive HCPs were asked to deliver 10 U of insulin using each method, and the amount discharged was weighed.

RESULTS

FlexPen was rated easier to use and overall more preferable than the syringe and vial by insulin therapy-naive HCPs (P < 0.001). The pen device was more accurate than the syringe and vial when used by experienced HCPs (mean +/- SD dose delivered, 9.91 +/- 0.11 U vs. 9.82 +/- 0.25 U, respectively; P < 0.001) and by insulin therapy-naive HCPs (9.91 +/- 0.12 U vs. 9.74 +/- 0.85 U; P < 0.001).

CONCLUSIONS

Insulin therapy-naive HCPs found FlexPen easier to handle and preferable to use compared to a conventional syringe and vial. Both insulin therapy-experienced and -naive HCPs were able to deliver insulin significantly more accurately with the FlexPen than with a syringe and vial (P < 0.001).

Force requirements and insulin delivery profiles of four injection devices

BACKGROUND

Injection force requirements for four insulin pen-type injection devices were evaluated using the AGS-IkNG Autograph force measurement device (Shimadzu Corp., Kyoto, Japan).

RESULTS

Compared with the Humulin Pen (the Japanese brand name is Humacart kit; the same device as the Humalog Pen; Eli Lilly, Indianapolis, IN), HumaPen Ergo (Eli Lilly), and NovoPen 3 (Novo Nordisk A/S, Bagsvaerd, Denmark), the InnoLet(Novo Nordisk) required the lowest injection force to both initiate piston movement and commence insulin delivery and required the lowest overall force throughout delivery. InnoLet and NovoPen 3 showed the most even load-displacement curves, suggesting a smoother delivery of insulin during injection. In contrast, the Humulin Pen and HumaPen Ergo demonstrated marked fluctuations in the force required to complete injection.

CONCLUSIONS

These performance characteristics appeared consistent with mechanical features of these insulin delivery devices, and the results highlight the potential importance of careful pen selection for patients with neuromuscular weakness or impaired manual coordination.

A useful cholesterol solvent for medical dissolution of gallstones

Dissolution of cholesterol gallstones by direct instillation of an agent into the biliary tract has been considered an alternate to surgical procedures. We developed an excellent direct solubilizer by combining d-limonene and medium-chain monoglyceride. This mixture enhances the advantages of each individual solvent and minimizes the disadvantages. In vitro experiments were done to determine the viscosities and the cholesterol dissolving rates of various combinations, and in vivo experiments were conducted to study their irritation effects on tissues. The optimal combination was a 3:2 mixture of d-limonene and medium-chain monoglyceride. It could quickly dissolve cholesterol gallstones with minimal or no observable side effect.