Impact of a Modified Needle Tip Geometry on Penetration Force as Well as Acceptability, Preference, and Perceived Pain in Subjects with Diabetes

BACKGROUND: Multiple factors impact subcutaneous insulin injection pain. Injection devices e.g., syringe or pen needle (PN) affect pain due to needle length, diameter, needle polishing and lubrication, and needle tip geometry. METHODS: We evaluated a modified 5-bevel PN tip in 32 G × 4 mm 31 G × 5 mm and 8 mm PNs vs the equivalent marketed 3-bevel PNs in laboratory penetration force testing, as well as in insulin-taking subjects for overall acceptability, comparative pain, and preference. The clinical tests were done in three ways: paired insertions with the subjects blinded to PN tip geometry, after brief at-home use of 5-bevel PNs, and again with subjects informed about each needle's tip geometry in paired insertions. RESULTS: Average penetration force in a skin substitute was 23% lower with the 5-bevel PNs vs similar 3-bevel PNs (p ≤ 0.01). In blinded testing and after at-home use, patients rated the 5-bevel needle as acceptable. After shortterm home use, patients rated the 5-bevel PN less painful and preferable to their usual PN (both p < 0.01). In paired, informed testing, the 5-bevel PN was less painful and preferred to subjects' currently used needles (p ≤ 0.01) and to other marketed PNs (p < 0.01). CONCLUSIONS: Needle tip geometry affects penetration force. When blinded, patients did not distinguish differences in PN tip geometry with fine-gauge PN insertions. A 5-bevel needle tip is perceived as less painful and is preferred by subjects following home use for usual injections. Similar results occurred when patients were informed that they were using a needle with a modified tip.