The Association between Needle Size and Waste Product and Its Effect on Cost-Effectiveness of Botulinum Toxin Injections?

Clostridium botulinum toxin (BT) must be administered intramuscularly with a syringe, but dead space in the syringe-needle complex may cause product waste and result in cost implications for the patient and provider. Syringe dead space is the volume of residual fluid that remains within the syringe after the plunger is fully depressed during medication injection. We calculated the average volume of remaining product in a syringe-needle complex and cost loss implication of this volume of BT. This is a single-center, analytical study using saline and four different sized needles for analytics of waste product and cost-effectiveness. Syringes of 1 mL with attached 18, 21, 30, and 32-gauge (G) needles, respectively, were compared. The syringe-needle complex was weighed before drawing 0.05 mL of saline. The fluid was then discarded with the appropriate syringe and then weighed again. This procedure was repeated for the four needle types and the average difference in weight of the syringe-needle complex before and after saline waste was measured. The volume was converted to units of BT used in clinical practice and the cost of waste product evaluated. The mean difference in needle-syringe complex weight before and after intervention was 0.068, 0.056, 0.04, and 0.026 g for the 18, 21, 30, and 32G needles, respectively. We found a statistically significant difference comparing the 18G with the 30 and 32G (0.02 and 0.0007, respectively) and comparing the 21G with the 30 and 32G (0.0042 and 0.00002, respectively). When we extrapolated the data to BT units (4U/0.1 mL), we found that theoretically 2.72, 2.24, 1.6, and 1.04 units of BT are left in the syringe-needle complex for the 18, 21, 30, and 32G syringes, respectively. At a cost of $6.01/U of onabotulinum toxin A, we then calculated a provider loss of a gross average (mean) revenue of $96 and 62.4 per 10 syringes used with 30 and 32G needles. Needle size used for drawing up and administering BT has an effect on the amount of waste product and subsequently on cost-effectiveness.