Abstract
Purpose: :
A 1cc tuberculin syringe with a half-inch long 30 gauge needle is typically used for intravitreal injection of a 0.05cc dose of Lucentis for wet AMD management. A previous study showed that this delivered a greater than intended dose. The tuberculin syringe and needle assembly also contain considerable "dead space", wasting medication. One-cc syringes are also manufactured with a half-inch long 30 gauge needle integrated into the syringe body, leaving very little dead space. This study compared dosing accuracy and drug wastage between the two different designs of 1cc syringes that may be used for intravitreal injections.
Methods: :
Fifty samples each of two different 1cc syringe designs were tested. The "integrated" design had the needle integrated into the body of the syringe. The "separate" design was a 1cc tuberculin syringe with a separate 30g ½ inch long needle attached. Syringes were weighed empty, with needle attached but covers removed, on an analytical balance with 0.1mg resolution. Each syringe was filled as accurately as possible with 0.05cc of sterile water, and weighed again after blotting the needle tip. The contents of the syringe was ejected, weighed, and converted to cc’s. The ejected volume was compared with that from an Eppendorf pipette, which served as a control. Each syringe was weighed again to determine the volume retained. Data from the two syringe designs were compared using a Student’s T test.
Results: :
The Eppendorf pipette control delivered a mean volume of 0.0500cc (+/- 0.0007cc). The integrated syringe design delivered a mean volume of 0.0516cc (+/- 0.0030cc), significantly different from the control (t=5.56, p=0.000). The separate syringe design delivered a mean volume of 0.0548cc (+/- 0.0027cc), also significantly different from the control (t=12.36, p=0.000). The integrated and separate designs delivered mean volumes that differed significantly from each other (t=5.60, p=0.000). The integrated design retained a mean residual volume of 0.0007cc (+/- 0.0050cc) while the separate design retained an average of 0.0790cc (+/- 0.0013cc). This difference was significant (t=30.49, p=0.000).
Conclusions: :
The two syringe designs are not interchangeable, and both delivered a volume in excess of that intended, although the integrated design was closer to the intended dose. The integrated design also retained less volume after injection. With Lucentis costing approximately $2000 per 0.2cc vial, $500 worth of medication is actually injected into the eye while almost $800 worth remains in the tuberculin syringe and is wasted. The integrated design retains only about $7 worth of medication. Significant cost savings could be realized by re-packaging Lucentis in pre-filled integrated design syringes.
Keywords: age-related macular degeneration • retina • injection