Patient Experiences With Injection Needles

It is estimated that there presently are about 370 million diabetics in the world, and the number is increasing, particularly in newly industrialized countries, such as China and India. Approximately 90% of diabetics have Type 2 diabetes, often caused by lifestyle, such as obesity and lack of exercise. 3-5% of diabetics have Type 1 diabetes, and the cause of the disease is unknown. The remaining 5-7% have either pregnancy diabetes (temporary illness), MODY ("Maturity-Onset Diabetes of the Young") or rarer forms of diabetes.

For the treatment of Type 1 diabetes, insulin has to be injected into the subcutaneous tissue from which it is taken up into the circulation. People with Type 1 Diabetes do not produce insulin and must thus inject insulin to stabilize blood sugar levels, typically via one or two daily injections with basal insulin, as well as so-called "bolus" injections at the time of each meal. This adds up to approximately 4-5 daily insulin injections. Type 2 diabetics, who are still "early" in the disease, have reduced sensitivity to the insulin they produce, so the pancreas overproduces insulin. Beyond lifestyle changes, treatment with metformin in tablet form will in this case be the first-line drug. In the later stages of the disease, the insulin production decreases and insulin therapy should be initiated, optionally in combination with a GLP-1 analogue (Glucagon-Like Peptide-1). It is estimated that only half of all people with Type 2 diabetes are diagnosed, and that half of those diagnosed are not in treatment. Worldwide, about 27% of the treated type 2 diabetic patients receive insulin treatment, or a GLP-1 analog, 1-2 times a day.

From the above figures it can be estimated that over 100 million diabetes injections are performed globally every day. In addition, other disorders also require subcutaneous administration of drugs, e.g. growth hormone therapy or inflammatory diseases such as rheumatoid arthritis or intestinal diseases. Thus, it is of great importance that the needles used for injections, are as painless and comfortable to use as possible.

The larger needle manufacturers have for many years sought to make needles less painful and to cause less skin trauma. Until recently, these measures have primarily been making needles thinner and shorter, but now needles with alternative grindings and needle tip designs are marketed. This is to compensate for the decreased robustness of the new very thin needles, which increase the risk of the patients damaging the needle tip during an injection. Little is known, however, of how these design changes influence the perception of pain, skin damage, etc.

Despite the large market for subcutaneous needles, the methods to test newly developed needles have remained the same for many years. One of the methods frequently used is a mechanical test where the needle is passed through a rubber strip, and the penetration force is measured. This method is rapid, reproducible and with very little variation, but there are no published data comparing the force measured in the rubber strip, with that measured in humans, and how or if the penetration force in a rubber strip relates to pain, discomfort, or other physiological parameters. Smith compares the insertion forces measured in the rubber strip and in a piece of cut off porcine tissue with the conclusion that these two behave very differently and that the rubber strip is estimated to be primarily useful in testing the needle lubrication and other friction-reducing parameters.