Occurrence of coring in insulin vials and possibility of rubber piece contamination by self-injection

Goring is reported to occur because rubber pieces are shaved off from a rub ber stopper when a needle is inserted into the rubber stopper of transfusio n liquid formulation. We verified whether coring really occurs in insulin v ials of self-injecting patients. We collected insulin cartridges from 30 ho spitalized patients and used the primary injection (trial injection), the s econdary injection and the cartridge remaining preparation as samples. We o bserved the rubber pieces using a microscope and measured the shape, number of pieces. The occurrence rate of coring was 73 % for the primary injectio n, 47% for the secondary injection and 97% for the cartridge remaining prep aration. The rubber pieces in the primary injection and the secondary injec tion which went through the needle are mostly in aggregate shape and the ru bber pieces in the cartridge remaining preparation which did not go through the needle are mostly in needle-like shape. A number of small rubber piece s are found in both the primary injection and the secondary injection, indi cating a high possibility that rubber pieces may be injected under subcutan eous tissue. The coring is considered to occur because needles are repeated ly inserted and rotated at the same spot. It is required to improve the str ucture to mount a needle to the pen-type injector in future. Goring is a ve ry serious problem from the medical and pharmaceutical points of view. Furt her study should be made on the implication to latex allergy and lipodystro phy.