Questions about needle reuse are raised in recommendations by the American Diabetes Association (1) and by practitioners and manufacturing companies (2). As an initial approach to examining these questions, we investigated whether multiple insertions of needles through the rubber stoppers on insulin vials would cause damage to needle tips (3). New needles were selected, attached to a precision manipulator, and inserted into insulin vials attached to a transducer that measured the force necessary to insert and remove a needle through the stopper. If needles were damaged by multiple insertions, an increase in force required to penetrate the rubber stopper would be expected.
In five experiments, we found that there was no significant difference in the mean force required to penetrate the rubber stopper of an insulin vial between 17 initial (41.5 g) and 17 subsequent (42.0 g) insertions. This suggests that needle tips are not dulled or damaged by multiple insertions to a degree that more force would be required to penetrate a vial stopper. Light micrographs and scanning electron micrographs supported the conclusion that little or no damage to needle tips occurred as a result of multiple insertions. We observed no hooks, bending, or other needle tip damage, although there was some evidence for deterioration of the silicon lubricant coating of needles.
At the same time, our examination of new, unused needles revealed imperfections when observed at high magnification. Our observations make it clear that damage attributed to reuse must be distinguished from inherent imperfections associated with the manufacturing process.
Clinical and manufacturer recommendations that discourage reuse of needles because of assumed dulling, bending, and/or fragmenting of needle tips are at variance with our findings, in which repeated penetration of insulin vial stoppers did not damage needle tips (2). Although we found no evidence of needle damage when penetrating the rubber stopper on insulin vials, there is need to ascertain the effect of cutaneous tissue penetration on needle tips. The reuse of needles by a significant number of patients with diabetes as a matter of convenience, or out of concern for cost and/or the creation of nonbiodegradable waste, indicates that further examination of needle reuse in vial stoppers and cutaneous tissue is warranted.
