Insulin injector

In this book we introduce major techniques used in designing and developing, roughly in the sequence in which they will be used. We show how techniques have been used (or could have been used) in a variety of products a laundry detergent, insulated windows, toothpaste, anti-fouling paint, an insulin injector, a powder coating, a box of matches, herbicide capsules, foamed snacks, a pharmaceutical tablet. Rockwool insulation, a ballpoint and a methanol catalyst. The authors have been involved in the development of several of these products. 

Insulin injectors deMver insulin under high pressure through the skin into fatty tissue without a needle. Insulin injectors can cause bmising, pain, and burning and are not indicated for children or the elderly. InsuMn injectors are expensive. 

Computed Tomography, Fig. 7 Inspection of assembled insulin injector. The CT scan allowed testing the operability and production quality of sample parts before going into serial production (initial sample inspection report), with typical tolerances of 50 pm and more than 300 inspection features per part (Courtesy of Volume Graphics GmbH)... 

H. OelschlRger A very severe problem of public health is the increasing number of patients who are suffering from diabetes. Do you see any chance of realizing the construction of an electrode which would be able, after implantation, to measure the glucose concentration in blood over a long period If you should succeed, then you would have solved the problem of the insulin injector. And I think that is more important than to measure dopamine concentration in rat brains ... 

H, Oelschlager May I add a further remark. We have had a Symposium on diabetes In Austria. I have learned from my physical collegues, who have long term experience, that the Insulin pump Is only to be handled by Intelligent patients. The personal behavior of the patient. Influences the success of the Insulin Injector. If diabetes could not be solved by an Injector coupled to a glucose sensor, only Intelligent people could benefit of such Insulin Injectors. 

II.f.1.3. Insulin delivery. Traditionally insulin was given intramuscularly and later subcutaneously. New technology has provided devices for insulin administrations including pen-devices, air powered injectors, external insulin infusion pumps (or continuous subcutaneous insulin infusion, CSII), and implantable insulin infusion pumps. Some novel forms of insulin delivery have been introduced, for example intranasal insulin gives peak insulin concentrations at 10-20 minutes after administration, but most insulin is still administered subcutaneously. 

To facilitate multiple subcutaneous injections of insulin, particularly during intensive insulin therapy, portable pen-sized injectors have been developed. These contain cartridges of insulin and replaceable needles. 

Lteif AN, Schwenk WF. Accuracy of pen injectors versus insulin syringes in children with type 1 diabetes. Diabetes Care 1999 22(l) 137-40. 

The closed-loop type artificial pancreas (specifically 8-cell), which consists of an automatic continuous monitor of blood glucose level (BGL) and an automatic injector of insulin which are coupled with feed-back system, has great potential for prevention of diabetic complication such as micro-angiopathies(l). A large-scale closed-loop type artificial pancreas for bedside use has already been developed and is clinically used at some laboratories and hospitals (2-4). However, this device is limited to only bedside use. On the other hand, the open-loop type artificial pancreas which consists of only a insulin injecting pump without an automatic continuous monitor of BGL, has been developed and is going to be clinically used(5-7). This system, however, can not completely control BGL as well as the bare pancreas in a normal body and often causes lower BGL(8-9). 

To facilitate multiple subcutaneous injections of insulin, particularly during intensive insulin therapy, portable pen-sized injectors have been developed. These contain cartridges of insulin and replaceable needles. Disposable insulin pens are also available for selected formulations. These include regular insulin, insulin lispro, insulin aspart, NPH insulin, and premixed 70%/30% and 50%/50% NPH/regular, 75% NPL/25% lispro, 50% NPL/50% lispro, and 70% NPA/30% aspart insulin. They have been well accepted by patients because they eliminate the need to carry syringes and bottles of insulin to the workplace and while traveling. 

Figure 8-1 Dial and pen injectors for insulin (on the same scale)...

The example we will use in this lesson is the selection of alternatives for treating the illness known as diabetes. This will lead to the most common method of this moment, where the patient treats himself with insulin injections. Figure 8-1 shows two current injector designs dial and pen . 

You might use throw-away insulin capsules with a septum that would avoid filling of the injector. 

Injection by the Patient If you want the patient to do the injections, the injector should preferably be portable and have an easy and accurate setting of the insulin dose. 

You have now chosen the concept for diabetes treatment and need to work it out. The real advance will be when patients can look after themselves, and keep correct insulin levels in their blood also during and after meals. You look on the Internet, read anything you get hold of, talk with doctors, nurses and patients, and even try out a few injectors on yourself You follow the experience of a few patients who are willing to try out the new method. You discuss what will be needed, and find out that the main requirements are ... 

We now start looking at devices and matter in our concept, starting with the new injector. The existing injectors are simple instruments as in Figure 8-8. The patient sucks up the required amount of insulin solution from a bottle (vial) and injects it at a suitable point and a suitable... 

All other ideas can be seen as details of these sub-projects. The sub-projects can be largely tackled independently, although there are interfaces. For example, the size of the insulin container will depend on the insulin concentration of the solution, and the needle does have to fit on the injector. 

Injection technique has pharmacokinetic consequences according to whether the insulin is delivered into the subcutaneous tissue or (inadvertently) into muscle. The introduction of a range of appropriate length needles and pen-shaped injectors has enabled patients to inject perpendicularly to the skin without risk of intramuscular injection. The absorption of insulin is as much as 50% more rapid from shallow i.m. injection. Clearly factors such as heat or exercise which alter skin or muscle blood flow can markedly alter the rate of insulin absorption. 

There are instances of older designs of needle-free injectors that, even with a well-characterized molecule such as insulin, show substantial differences between needle-free and needle delivery. However, improvements in the understanding of the aforementioned principles as well as advancements in the design of needle-free injectors have led to the recent reporting of improved clinical data. Table 1 summarizes an incomplete list of drugs for which there exist clinical data from needle-free administration, all of which demonstrated broadly similar performance between the needle-free system and the needle system (not every report provides sufficient data to determine if bioequivalence was demonstrated). 

Kerum, G. Profozic, V. Granic, M. Skrabalo, Z. Blood glucose and free insulin levels after the administration of insulin by conventional syringe or jet injector in insulin treated type 2 diabetics. Horm. Metab. Res. 1987, 19, 422-425. 

Halle, J.-P. Lambert, J. Lindmayer, I. Menassa, K. Coutu, F. Moghrabi, A. Legendre, L. Legault, C. Lalumiere, G. Twice daily mixed regular and NPH insulin injections with new jet injector versus conventional syringes pharmacokinetics of insulin absorption. Diabetes Care 1986, 9, 279-282. 

Diabetics have traditionally been forced to perform self-injection, so auto-injectors have been developed for use in this area and look like a modem felt-tip pen. Quantities of insulin can be pre-set by turning a knob on the pen which has features including an audible click, clear resistance prior to each dose and a visual indication on the scale thus helping to eliminate dosing errors. Quick and easy dosing is possible with such systems. Auto-injectors are marketed by a number of companies under the following tradenames Novopen , Novepen II, NovoLet , Optipen II and D-Pen . Pressurised needleless systems are also now available. 

The nurse is teaching the client with Type 1 diabetes how to use an insulin pen injector. Which information should the nurse discuss with the client ... 

Discuss that the insulin pen injector must be used in the abdominal area only. 

Explain that the traditional insulin syringe is less painful than the injector pen. 

The insulin pen injector does not require drawing up insulin in a syringe. 

The insulin pen injector can be used in any subcutaneous site that traditional insulin can be injected. 

Jet injectors deliver insulin transcutaneously by an air-jet mechanism. The insulin solution or suspension is forced at high pressure through a fine nozzle, penetrates the skin without a needle, and creates a multitude of small depots. The dispersion of insulin deposited in the tissue explains the more rapid absorption of both rapid- and retarded-acting preparations (Taylor et al, 1981 Malone eta/., 1986 Houtzagerse/a/., 1988). Jet injection seems to affect the action profile of NPH insulin more markedly than that of the Lente t e insulins (Houtzagers et al, 1988). These devices are not painless and, in a European study, not well accepted by patients irrespective of the presence or absence of needle phobia (Houtzagers etal, 1988). However, in a more recent American study, the majority of patients preferred to take insulin by jet injector compared to needle injection (Denne et al, 1992). Jet injection has been found to be associated with a diminished antibody... 

Denne, J. R., Andrews, K. L., Lees, D. V., and Mook, W., 1992, A survey ofpatient preference for insulin jet injectors versus needle and syringe. Diabetes Educ. 18 223-227. 

GaU, M.-A., Mathiesen, E. R., Skott, P., Musaeus, L., Damm, S., Beck-Nielsen, H., and Parving, H.-H., 1989, Effect of multiple insulin injections with a pen injector on metabolic control and general well-being in insulin-dependent diabetes mellitus. Diabetes Res. 11 97-101. 

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