Background: Retained botulinum toxin solution may be visible in vials and syringe tips after mixing and presumed complete injections, leaving patients without the full prescribed dose.
Objective: To quantify the mean amount of retained toxin within vials, syringes, and needles following spasticity injections (phase 1) and to design/test a targeted intervention for reduced retained toxin (phase 2).
Design: Prospective cohort quality assurance study.
Setting: Outpatient spasticity program in a rehabilitation facility.
Participants: Nine physicians specializing in physical medicine and rehabilitation, performing successive mixing and injections for spasticity with onabotulinumtoxinA or incobotulinumtoxinA.
Methods: After initial review (phase 1), recommendations were made (phase 2) including not inverting the vial to withdraw medication unless needed, favoring 2-mL dilutions when possible, and decapping of vials for more complete medication withdrawal.
Main outcome measurements: Retained volume of toxin solution that was not injected and estimated retained units of toxin.
Results: A total of 157 vials of botulinum toxin A were tested. Of the 82 initial, phase 1, preintervention vials (8200 units), 5.5% (∼452 units) of toxin solution was retained following mixing and injections. One and 3-mL syringe tips contained a mean of 3.32 and 1.44 units of toxin respectively. Within vials, saline dilutions with 2 mL contained less mean retained toxin (1.89 vs 3.31 units) relative to 1-mL dilution. Awareness of monitoring significantly decreased retained solution in vials (0.035 mL vs 0.069 mL for naïve group, P = .002). Phase 2, postintervention testing of 75 vials demonstrated that withdrawing toxin from the inferior edge from a non-inverted vial reduced the retained toxin by 32.8% (P < .001). Decapping the vial further reduced the mean retained toxin to 0.42 units per vial (81.9% reduction, P < .001).
Conclusions: A potentially clinically significant amount of botulinum toxin solution is retained following mixing and injections. Implementation of guidelines significantly decreased wasted botulinum toxin.
Level of evidence: III.
Copyright © 2018 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.