title: Bupivacaine-induced myotoxicity and its effect on botulinum toxin paresis.
abstract: OBJECTIVE
  To determine the effect of the coinjection of bupivacaine with botulinum toxin type A on the degree of muscular paralysis. Enhancement of paralysis could allow a decreased dose of neurotoxin treatment, thus reducing the risk for neutralizing antibody formation.
  
  
  METHODS
  Prospective, randomized, double-blind study. Sixteen consecutive patients undergoing treatment of glabellar furrows received botulinum toxin A reconstituted with bupivacaine 0.75% to one corrugator muscle and botulinum toxin A reconstituted with nonpreserved normal saline to the contralateral muscle. Patients were evaluated on days 0 (injection day), 3, 7, 30, 60, and 90. Patients also completed a questionnaire each visit regarding their assessment of paralysis, asymmetry, and adverse effects.
  
  
  RESULTS
  At 1 week after botulinum toxin A injection, 68.8% of the patients showed greater weakness on the bupivacaine-reconstituted side as opposed to 25.0% of patients showing greater weakness on the saline-reconstituted side. At 1 and 3 months, there was no statistical difference in weakness between the saline and the bupivacaine sides. The survey revealed that 56% of the patients had greater pain on the saline side, 31% on the bupivacaine side, and equal pain in 13%.
  
  
  CONCLUSIONS
  Reconstituting botulinum toxin A with bupivacaine is safe, does not limit efficacy, and does not reduce the degree or relative duration of muscular paralysis. Reconstituting botulinum toxin A with bupivacaine results in faster onset of paresis, possibly due to a synergistic effect of bupivacaine induced myotoxicity. Utilizing bupivacaine may result in less pain for patients.
authors.affiliation: Cullen Eye Institute, Baylor College of Medicine, Department of Ophthalmology, Houston, TX 77030, USA. myen@bcm.tmc.edu
authors.forename: Michael T
authors.initials: MT
authors.lastname: Yen
authors.forename: Victoria K
authors.initials: VK
authors.lastname: Wall
mesh_terms: D000779:Anesthetics, Local / Q000008:administration & dosage*; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D002045:Bupivacaine / Q000008:administration & dosage*; D004357:Drug Synergism; D005260:Female; D006801:Humans; D008297:Male; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D010291:Paresis / Q000139:chemically induced*; D011446:Prospective Studies
chemical_list: D000779:Anesthetics, Local; D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A; D002045:Bupivacaine